Mortise Gauge

identity

• Name: Mortise Gauge (British spelling: mortice gauge, or morticing gauge — a clean Anglo/American spelling variant confirmed across manufacturer and retail sites on both sides of the Atlantic, not a naming collision) [MOG1][MOG2].
• Family / category: Layout and Marking Tools → edge-referenced scribing gauges, the twin-pin sub-family. Sits beside the corpus's own Marking Gauge (single pin) as a functional development of the same family; Sellers's pin-count taxonomy below is one useful teaching convention, not binding market nomenclature.
• One line: An edge-referenced gauge that establishes two parallel scribe lines at a controlled spacing, most commonly the width and offset of a mortise and its mating tenon. The classic Western wooden form has a fence and two points, often one fixed and one sliding on an internal rod; other forms use independently adjustable rods or wheel cutters, two beams, or fixed-width pin pairs. It preserves a chosen spacing and reference offset, which reduces transcription error between repeated mortises and tenons. It improves consistency; it does not guarantee fit, because reference-face choice, waste-side orientation, locked settings and cutting accuracy still govern the joint.

✦ how NOT to use it

The heaviest section.

not-for (jobs it is a poor fit for)

• Joints that need only one boundary line. Mortise-and-tenon work is the primary use; for a single-line joint such as a dovetail baseline a plain marking gauge or a square is simpler, and a second point can get in the way. This is a preference, not a ban: other repeated two-line layouts (grooves, rebates, dados, offsets) can be valid where the cutter geometry and fence access suit them. Confidence: MEDIUM (reasoned from the mechanism; per the reviewer, the Veritas maker page supports wider two-dimension use).
• Curved or non-straight-edge stock. The fence needs a true straight reference; on a curve it touches at one rocking point and the scribed distance from the edge varies continuously — the same registration-geometry limitation the parent Marking Gauge entry already documents, inherited whole here. Confirmed independently this run by a named forum voice (Lataxe, Fine Woodworking 2008): "Not all the traditional gauges are good for marking agin' a curved edge" [MOG20]. Confidence: MEDIUM-HIGH.
• Machine- or jig-referenced joinery, where the workflow is already fully controlled. Where a router jig, a hollow-chisel mortiser's fence or a Domino joiner registers the joint off the machine, the gauge is often optional rather than categorically useless; it may still serve for verification, shoulder or cheek layout, or hand-fitting alongside machine-cut work. Also a poor fit: inadequate fence registration, inaccessible edges, or unsuitable cutter geometry. Confidence: MEDIUM-HIGH.

dangerous (ways it injures the user)

Rebuilt in the 2026-10-16 fix pass. The original called this class "thin/benign" because no injury account was found. That was a search result, not a risk assessment, and is withdrawn.

Hazard. A mortise gauge exposes one or more sharp pins, knife points or wheel cutters. The ordinary hazards are puncture or laceration from the exposed points, the gauge slipping into the holding hand, unstable or small work, and unintended contact during storage, adjustment or while setting from a chisel. CCOHS treats unintended contact with sharp cutting tools as an ordinary injury risk (CCOHS sharp-blades and general hand-tool pages, read 2026-10-16) [MOG29][MOG30]. The Veritas gauge makes its cutters retractable for storage, which shows exposed cutters are a hazard the design itself addresses [MOG5].

Controls.

• Inspect before use. Check the pins or cutters for damage and the fence and pin locks for security; repair or replace damaged tools [MOG30].
• Support the work. Hold it in a vise or on a stable bench or slip-resistant surface, and clamp small pieces. Do not hold the workpiece in the palm while scribing [MOG29][MOG30].
• Hand position. Keep the non-guiding hand out of the scribing path and out of the path the gauge would take if it slips; never cut toward the body [MOG29][MOG30].
• Light, controlled strokes. Excessive pressure raises the chance of a slip; a light first pass is also the correct marking technique [MOG29][MOG19].
• Protect the points. Retract, cap, sheath or otherwise cover the points where the model permits, and cover sharp edges when the tool is not in use [MOG29][MOG30]. Where a model offers a retractable cutter (Veritas), retract it after use [MOG5].
• Store so points cannot be contacted. Do not leave the gauge pins-up on a bench or hidden under rags; keep it in a rack, drawer or toolbox where exposed points cannot be reached, and point exposed edges away from aisles [MOG29][MOG30].
• Eye protection when dressing, filing or sharpening, where the maker permits those operations (see the dressing caution in correct use) [MOG30].
• Follow the maker's instructions for sharpening, replacement and cutter orientation for the exact gauge. The Veritas Care and Use PDF was not reached in this pass [manual, relayed].

One user's anecdote. SARGEgrinder47's account of disabling a spare pin with silicone and duct tape [MOG17] shows an exposed spare point worried one user with a medical reason to avoid punctures. It is not evidence for or against a general hazard grade, and improvised adhesive or tape is not a recommended method; use the maker's retraction, removal, cap or storage method, or a dedicated single-purpose gauge.

Evidence scope. No tool-specific injury statistics were located in the original run. That absence is not used to grade the hazard. Confidence: MEDIUM-HIGH for the general sharp-edge hazard and controls (government safety authority); not model-specific.

damaging (ruins the tool or the work)

• For hand-chopped mortises, setting the point gap by ruler or nominal size instead of the actual chisel steel. The most-repeated discipline violation across the named sources of the original run — Rod Sheridan, Derek Cohen, and the Dean J./Frank D. forum exchange all converge on it, and Neal's own finding (his real chisels didn't match a factory-cut nominal width) is the sharpest evidence of why it matters [MOG7][MOG16][MOG17]. Confidence: HIGH.
• Faint or uneven lines. Causes include fence rocking, unequal pressure, cutter orientation, burrs, dullness, a loose adjuster, a bent pin, grain direction, or a real height mismatch. A retailer teaching note suggests checking that both pins are at the same height and, if they are not, filing one down slightly [MOG26]. That note is for that retailer's gauges; it is not carried forward as a general instruction here, because filing can permanently alter a fixed or replaceable cutter's geometry. Diagnose first and dress a pin only as the maker specifies (see correct use). Confidence: MEDIUM.
• Beam/pin-mechanism racking. Inferred from Follansbee's own detailed account of an antique gauge's keyed anti-rack pin-and-groove system — direct evidence that period makers actively engineered against this failure mode, meaning it was a real, recognized problem worth building hardware to prevent [MOG9]. Confidence: MEDIUM (mechanically sound, inferred from engineering evidence rather than a documented failure account).
• Running the gauge off the end of a board. A directly-fetched retailer teaching note recommends working from both edges toward the middle rather than running the full length in one pass, to avoid splintering at the far end [MOG26]. Confidence: MEDIUM-HIGH.
• Over-sharpening the pins to a fine point. A counterintuitive, named finding: an overly sharp pin can be harder to control and leaves a line that's actually harder to clean up later; several forum voices deliberately keep their pins slightly blunt [MOG20]. This is a forum preference about line control, not a safety instruction; blunt or sharp, the points still puncture. Confidence: MEDIUM (forum-sourced).

beginner-trap (mistakes that look fine until they aren't)

• Trusting a stamped or nominal chisel width instead of physically cross-checking it against the actual steel (for hand-chopped mortises). Neal in San Jose's own finding — even a factory-cut, fixed-width cutter didn't match his real chisels — is the sharpest sourced evidence for this trap [MOG16]. Confidence: MEDIUM-HIGH.
• Mixing layout methods. A forum correction (Sawmill Creek's mike holden) suggests marking from each side and splitting the difference to check centring. That is a particular design method for a centred mortise in uniformly thicknessed stock, not a universal correction; on stock with thickness variation it can create doubled or widened lines and defeats reference-face logic. Choose one method per project: mark every mating part from the designated face and edge, or verify a deliberately centred mortise from both faces. Confidence: MEDIUM.
• Imitating an expert's clean result without the underlying technique. Named directly by Derek Cohen regarding novices copying Rob Cosman's DVD technique without the light touch behind it [MOG17]. Confidence: MEDIUM-HIGH (named, but a single source).
• The tool "looks simple, is deceptively fussy for a first-timer." Directly evidenced by "wilbur"'s own first-person account of abandoning the gauge for pencil-plus-single-pin after struggling with it [MOG16]. Confidence: MEDIUM (single first-person account, consistent with Sellers's own teaching emphasis on technique).

lineage-misuse (treating it like its ancestor or its sibling)

• ★ Overlapping names: mortise gauge, combination gauge, mortise/marking gauge. Paul Sellers states a strict pin-count taxonomy and warns that many gauges listed as mortise gauges are combination gauges [MOG3]. Current makers and retailers also legitimately use "mortise/marking gauge" for a 2+1 tool (Lee Valley listing, per the reviewer [manual, relayed]). The practical rule for matching and search: treat the three as overlapping market terms and read the pin arrangement from the product description, which this entry records as a field rather than as a mandatory public name. Sellers's taxonomy is kept as one useful teaching convention, not as proof that the market is wrong. Confidence: HIGH that the names overlap; the taxonomy is a convention.
• The patent-record collision. US 1,432,485, titled "Mortise gauge" but actually a door-lock-mortise installation jig with no scribing function at all [MOG13] — anyone tracing this tool's own patent history through a plain keyword search will hit this false positive. A second, adjacent family — the "Butt and Mortise Gage" patents (1890/1911/1916) — covers unrelated door-hardware layout tools that also carry "mortise" in the name [MOG14]. Neither is this tool; both share its name closely enough to mislead a researcher, worth flagging to any future run or research pass doing patent-record work on this tool. Confidence: HIGH (directly fetched and read).
• Using it as if it were the plain marking gauge — the ancestor's own failure, reintroduced. Setting only one point and ignoring the other reduces the tool to a single-pin gauge, with the resetting risk that a twin-line gauge exists to reduce. Confidence: MEDIUM (reasoned directly from the parent entry's own documented mechanics).

correct use

The deep operation belongs to Reed; this is the short version.

• For a hand-chopped mortise sized by a particular chisel, set or verify the spacing from that actual chisel rather than trusting its stamped nominal size. Holtzapffel (1846), Sellers, Cohen and Cherubini converge on this for hand work, and Neal's finding (a factory-cut Tite-Mark blade that didn't match his real chisels) shows why [MOG3][MOG16][MOG17][MOG7]. When another process controls the mortise (router bit, machine, loose tenon, standardized part, drawing), set from the actual cutter, a test cut, the mating component, or the verified design dimension. Contact safety when setting from a chisel: do not force a sharpened edge between the points or put fingers against the edge; use the maker's demonstrated contact point and a non-cutting portion of the blade where the design permits (per the reviewer's safety notes, [manual, relayed]).
• Register from the face side, exactly as the parent Marking Gauge entry's own correct-use section already states. Mark every mating part from the designated face and edge; this discipline is inherited, not tool-specific. Orient single-bevel cutters toward the waste; "trail the tip" is not necessarily the same instruction for every cutter geometry.
• Test on scrap and check both lines scribe evenly before starting the job. With two points, one crisp line and one faint or absent one can have several causes: fence rocking or unequal pressure, a loose adjuster or pin, cutter orientation, a burr or dull point, a bent pin, grain direction, or a real height mismatch. Do not press harder to compensate. Diagnose before altering anything: check fence registration, pin security, cutter orientation, burrs and the maker's instructions [MOG26].
• Do not file or grind a pin as a first response. Dressing the points changes geometry, bevel orientation and projection, and some cutters are hardened or replaceable. Only if the manufacturer specifies dressing: secure the gauge, protect the other point, wear eye protection, use a handled file or suitable abrasive, preserve the specified bevel and lead geometry, deburr, manage the filings, and retest on scrap. Replace or have serviced a bent, loose or damaged cutter. The retailer note that suggests filing one pin [MOG26] is a teaching note for that retailer's gauges, not a model-independent procedure.
• Light first pass, firm fence registration, deepen if needed — the same discipline the parent entry documents for the single-pin form [MOG19]. Keep the non-guiding hand out of the scribing path and cut away from the body.
• Do not mix layout methods mid-project. For reference-face joinery, mark every mating part from the designated face and edge. If the design specifically calls for a centred mortise and the stock is uniformly thicknessed, verify the centre from both faces or use a centre-setting method; do not mix the two approaches.

✦ matching

The workbench's first read.

does: Preserves a chosen spacing and reference offset for the two boundaries of a mortise or its mating tenon, reducing the transcription error of resetting between repeated mortises and tenons [MOG7][MOG6]. Classic simultaneous twin-pin gauges may mark both lines in one traverse. Independent dual-wheel gauges mark one line at a time and may need a cutter-orientation or setting change between mortise and tenon work [MOG28]. For a hand-chopped mortise the width can be set from the chisel itself. Layout improves consistency but does not guarantee fit. Some bodies (the 2+1 type) also carry a single marking pin on the reverse face [MOG3].

suits: Mortise-and-tenon layout is the primary use — furniture-frame joints and, as plausible uses inherited from the Mortise Chisel entry and not directly sourced for the gauge, chair and table leg-to-rail construction, sash work and timber framing; any hand-tool joinery workflow where layout precedes hand-chopped or hand-pared work. Other repeated two-line layouts (grooves, rebates, offsets, thickness transfer) can be valid where cutter geometry and fence access suit them; the Veritas maker page says its dual gauge can be used wherever repeated marking of two dimensions is required (per the reviewer, [manual, relayed]).

kit-fit:

• Pairs with: the Mortise Chisel — the defining relationship for hand-chopped work; the points are set or verified from that specific chisel, not a catalog width. Depending on workflow, also router bits and test cuts, mating loose tenons, and verified specifications.
• Substitutes for it: a single-pin Marking Gauge can lay out the same two parallel boundaries in two settings, but resetting adds an opportunity to mis-state the spacing or lose the intended offset. Two locked marking gauges are another practical substitute, as are knife-and-square layout and a model-specific dual-wheel attachment.
• Can be substituted by: a wheel-gauge mortise attachment for makers who already own a wheel gauge and want clean scribing in both grain directions without a dedicated tool [MOG4].
• Cannot replace, and does not compete with: the corpus's own Hollow-Chisel Mortiser or Domino Joiner — both of those cut the joint; this tool only marks it. No sourcing found in the original run suggests market confusion on that boundary.

access: A modest step up from the plain marking gauge for anyone already comfortable with one — the added move is simply laying the chisel between the pins and locking the slide before gauging, which Tools For Working Wood and Sellers both present as a basic, teachable first step rather than an advanced skill [MOG24][MOG3]. The realistic beginner trap (see below) is trusting a stamped or nominal chisel width instead of the actual steel. Safety: sharp pins or wheels can puncture or cut; see dangerous below for the hazards and controls. No tool-specific injury statistics were located, and that absence is not evidence that the hazard is small.

revival: The mortise gauge's case for a modern maker is the same "transfer, not measurement" argument the parent entry already makes for the family as a whole — but sharper here, because the failure mode it removes (two mismatched settings) is a genuine, common source of a mortise-and-tenon joint that simply doesn't close square. For hand-chopped work, reading a number off a chisel and dialing it back in adds transcription steps that setting from the chisel itself avoids [MOG7][MOG16]. Where another process or a drawing controls the joint, a verified dimension or test cut is the controlling reference.

anatomy

• Anatomy below describes the classic Western wooden twin-pin gauge. It is not the whole category; see variations for independent-rod, wheel-cutter, two-beam and fixed-pair forms.
• Beam / stem — the bar carrying both pins, typically square in section on quality wooden gauges [MOG22]. Design reasoning (not established by the cited encyclopedia): a square beam may resist twisting under the extra torque two pins introduce.
• Fence / stock / head — slides on the beam, registers against the reference edge; brass-faced or brass-plated on premium models [MOG23].
• Fixed pin — in the classic form, set permanently at the beam end.
• Sliding pin — in the classic form, mounted on an internal rod inside the beam, moved to set the mortise width. Two mechanisms of this classic form in current manufacture, per a manufacturer/retailer product description: a simple brass slide/post ("standard" mechanism) or a threaded rod plus a separate brass thumbscrew ("deluxe"/screwslide mechanism) for finer, more repeatable control [MOG24].
• Locking thumbscrew — locks the fence's position on the beam; a separate control from the sliding-pin adjuster above, so a gauge typically carries two independent thumbscrews doing two different jobs [MOG22].
• Brass wear strips / wear plug — inset in the fence face on quality gauges, slowing the same crowning-wear failure the parent Marking Gauge entry documents (Cherubini's worn-fence finding, [MG24]) [MOG23].
• Mechanical logic, stated plainly (classic twin-pin form): two independent adjustments stack — (1) fence-to-beam distance sets the offset from the reference edge; (2) sliding-pin-to-fixed-pin distance sets the width, set for a hand-chopped mortise by presenting the actual chisel to the points rather than measuring. This is exactly the mechanism Nicholson's 1812 §60 already describes, confirmed unchanged in current manufacturer literature [MOG25].

(No labeled manufacturer parts diagram was directly fetchable as a static image this run — flagged as a Forge image gap, below, rather than invented.)

variations (living)

trades

• Joinery / cabinetmaking — the home trade, unbroken from Nicholson's 1812 text to today's teaching canon.
• Wheelwrighting — the Science Museum Group's own object (1949-336/11) documents a wheelwright's mortice gauge in that trade, via R. A. Salaman's collection; per the reviewer the text record establishes trade association and physical existence, not the detailed pin mechanism or a manufacture date [MOG21].
• Chairmaking, sash-and-door, timber framing — plausible uses, inherited from the corpus's own Mortise Chisel entry; not directly sourced for the gauge.
• Adjacent, unrelated trade — flagged, not this tool's own: door-hardware installation and site carpentry use tools patented under the near-identical name "Butt and Mortise Gage" (above) for hinge-mortise layout — a real, separate trade family that shares this tool's name but not its mechanism or its joinery job.

lineage

Ancestors

• The corpus's own Marking Gauge — the single-pin form this one is a functional development of (a family relationship; this entry does not claim a documented line of developmental descent). Its own "history" section states the mortise gauge's reason for existing in one sentence: "Two independent gauge settings for two mortise walls means two opportunities for error and zero guarantee of parallel. The two-pin gauge with a sliding inner pin makes the pair a single setting." This entry inherits that thesis for the traditional twin-pin form rather than re-deriving it — see Marking Gauge for the full ancestor/Petroski arc.
• Behind the marking gauge: free-hand scribing (awl, marking knife run against a fingertip fence) — the same ancestor line the parent entry already documents.

Descendants / siblings (the living family)

• Combination gauge / "mortise/marking gauge" — adds a third pin (a single marking pin on the reverse face) to a twin-pin face, so one body does both jobs (Stanley No. 77/No. 65/No. 90 class). Paul Sellers gives a clear practitioner taxonomy: "A single pin gauge is a marking gauge, twin pin versions a mortise gauge and with the extra triple pin, 2 on one side, 1 on the other, a combination gauge" [MOG3]. Current makers and retailers also legitimately sell 2+1 tools as "mortise/marking gauge" (the reviewer, relayed from the Lee Valley listing [manual, relayed]), so the three names overlap in the market; this entry states the pin arrangement explicitly for each product rather than treating one name as the only correct one. See lineage-misuse, below.
• Wheel-gauge mortise attachment — a modern, non-pin reinterpretation: a bolt-on accessory (Taytools' "Wheel Marking Gauge Double Mortise Attachment Set") that fits an 8mm-shaft wheel gauge and scribes both mortise walls with round cutters instead of pins, current retail product, not a standalone tool [MOG4].
• Veritas Dual Marking Gauge / Dodeca Gauge — modern precision reinterpretations using twin independently adjustable stainless rods on an aluminum/brass body rather than a traditional wooden beam-and-fence. Read directly in the 2026-10-16 fix pass (Veritas product page): each rod has its own setting and thumbscrew lock, the two wheel cutters are replaceable and retract into the brass face for storage or to use one cutter alone, and an optional shaft clamp locks the rods' relative position so a size can be repeated at different offsets [MOG5]. The Dodeca claim that its spacing "makes it easy to set mortise widths directly from your chisels" remains search-summary level.

Contemporaries

• The corpus's own Mortise Chisel — not a rival tool but the instrument this gauge is set from; the two are functionally a matched pair, the same relationship the Mortise Chisel entry itself documents opposite the Bench Chisel.
• The plain Marking Gauge used twice, at two separate settings — a real, still-practiced substitute (see matching → kit-fit), carrying the resetting risk (mis-stating the spacing or losing the offset) that the twin-line gauge exists to reduce.

history

The named-category anchor — Nicholson, 1812. Retrieval chain: the quotation below was retrieved in an earlier run and cited through the Marking Gauge entry [MG2]; it is not a newly linked primary scan in this entry. The Mechanic's Companion, §60, "The Mortice Gauge," gives the tool its own numbered, systematic description in the same 1812 text that names the plain gauge in §59 (already the corpus's earliest named-category anchor, via Marking Gauge): "two teeth instead of one. One tooth is stationary at the end of the stem, and the other is moveable in a mortice between the fixed tooth and the head… The use of this gauge is as its name implies, for gauging mortices and tenons" [MOG6]. This is the load-bearing text for this entry specifically — by 1812 the twin-pin form was a named instrument with its own description.

The set-from-the-chisel discipline — Holtzapffel, 1843–46. Retrieval chain: secondary quotation via Jansa [MG4], not a newly linked primary scan. "Frequently the mortise chisel is slightly stuck into the work to imprint its own width, by which to adjust the gages; and every piece is gaged from the face side" [MOG7]. Both halves of that sentence remain common hand-tool teaching today for hand-chopped joinery, and two named living practitioners describe the same practice (see human side).

The Seaton chest, 1796 — an early documented physical solution to the tool's own resetting problem. Benjamin Seaton's tool chest (Guildhall Museum, Rochester) contains a mortise gauge with four sets of fixed pins, each pre-spaced to match a specific mortise chisel already in his own kit — a one-owner answer to the fact that resetting a single sliding-pin gauge mid-project risks losing a good setting [MOG8]. It is the oldest dated example of that solution found in the original run; no comprehensive search was made, so nothing stronger is claimed.

A second, independently documented solution — the wedged sliding gauge, reverse-engineered by Peter Follansbee (2022). Follansbee bought an antique two-beam, wedge-locked mortise gauge at the Brimfield Antique Show and wrote up its mechanism in detail: a keyed pin-and-groove system stops the two sliding beams from racking out of alignment with each other, and two scribed reference lines let the user "preset" three common mortise widths (3/8″, 7/16″, 5/16″) by realigning marks rather than resetting from scratch [MOG9]. A third engineering answer — after Seaton's swappable pin-sets and, a century later, Stanley's brass-shoe/split-shaft mechanism (below) — to the same underlying failure: a sliding pin that won't reliably return to a good setting.

The patent era. Two patents were directly fetched and read; a third citation inherited from the parent entry required a correction.

• GB-184,700,970, Fenton & Marsden, Sheffield, dated Feb 13 1847 [MOG10] — an early documented English mortise-gauge reference, already cited in the Marking Gauge entry. Described exactly, this is a reported 1847 application or stamped patent reference, not a confirmed grant: DATAMP's record (direct fetch in the original run) says no finalized specification or drawing survives. The date is known only because it is stamped on surviving physical Fenton & Marsden gauges, cross-referenced against period British patent numbering (970th patent of 1847) [MOG10]. Company lineage, also directly confirmed: Fenton & Marsden (est. 1839) → Fenton bought out 1846 → Marsden Brothers & Silverwood → Marsden Brothers (~1852–54) → John Wilson, Marsden Brothers (1896) → absorbed by Robert Sorby & Sons (1901) [MOG10].
• US 132,421, "Split-shaft Mortise Gage," Justus A. Traut, Stanley Rule & Level Co., granted Oct 22, 1872 [MOG11] — covers the brass "gib" protecting the beam from the retaining screw, plus the captive-slider split-shaft construction; DATAMP's own record states both ideas "were used on Stanley tools for over 80 years" and the brass shoe "is still in use on many gages to this day."
• Correction to the parent entry's citation, flagged rather than silently fixed. Marking Gauge cites US 36,973 (Traut, 1862) as a "Stanley two-arm mortise gauge patent." A direct fetch of DATAMP's own record this run shows the patent is titled "Carpenter's Bench Gage" and is classified simply under general marking gauges, not as mortise-specific [MOG12]. The underlying Traut/Stanley mortise-gauge lineage still holds via US 132,421 (1872, above); only the specific 1862 attribution needs a precision pass on the parent entry.

A genuine naming collision inside the patent record itself. US 1,432,485, "Mortise gauge," Edward A. Moller, filed 1920, granted 1922 — fetched and read in full [MOG13]. Despite its literal title, this is not a scribing tool at all: it's a clamp-and-guide jig that bolts onto a door edge to guide an auger and chisel while cutting a lock mortise. Anyone searching patent records for "mortise gauge" hoping to trace this tool's own history will hit this false positive first — flagged prominently here and carried into lineage-misuse, below. A second, separate naming lineage compounds the risk: three "Butt and Mortise Gage" patents (US 432,328, 1890; US 985,504, 1911; US 1,197,308, 1916; all confirmed via DATAMP) [MOG14] cover door-hardware/hinge-mortise layout tools for site carpentry — a real, dated, unrelated family that also uses "mortise" in its name.

Later reception of Seaton's solution. Dean Jansa's "Mystery of the Marking Gauge" (Popular Woodworking, Dec 2006) — already cited in the parent entry [MG4] for its Moxon/Holtzapffel quotations — is cited in three woodworking forums (WoodCentral 2007, Fine Woodworking 2008, Sawmill Creek 2009) [MOG15][MOG16][MOG17]. The article was cited by several later forum discussions and appears to have encouraged shop-made, chisel-matched pin-sets modeled on the Seaton chest. Forum repetition shows reception among specific posters; it does not establish that one article caused a generation-wide revival.

Commercial continuity, honestly graded. Stanley No. 90 ("Williams Patent," c. 1859–1879), No. 93 (1911–1943, marketed as a combined butt/marking/mortise gauge), and No. 77 (the combination-gauge class, Sweetheart-era, listed at $1.60 new in period catalogs) are real, collector-traded objects — but this run's sourcing for their specific dates and catalog details rests on dealer/collector listings (Jim Bode Tools, Worthpoint, eBay) rather than a primary Stanley catalog scan, and is held at reduced confidence accordingly [MOG18]. Marples's own current-production continuity (below, proof of existence) is directly confirmed; a specific 1873/1928 Marples catalog claim reached this run only via search summary and is not cited as fact.

✦ human side

Named hands — technique.

• Paul Sellers, two posts fetched in full [MOG3][MOG19]. Supplies the entry's load-bearing taxonomy (above) and its clearest sourced naming-collision warning: "Many gauges listed or described as mortise gauges are often combination gauges or not mortise gauges at all." On mechanism: mortise-gauge pins are stouter and set at a shallower angle than a plain marking gauge's pin, because of the heavier end-grain tenon work the tool does; twin-pinned gauges "are often problematic because they are difficult to sharpen to equal heights," and that his own preferred practice, on his own gauges, is to shape both pins to matched flat chisel-edge bevels rather than a round point. That is Sellers's workshop method, not a general repair instruction for any gauge; see the dressing caution in correct use. On use: the core beginner failure is "bulldogging" the tool with too much downward pressure instead of a light touch.
• Derek Cohen (Perth, Australia), directly fetched across three forum threads [MOG16][MOG17][MOG20]. Signature technique: press the actual mortise chisel into the wood to leave witness marks, then set the gauge pins directly into those marks — "there is no substitute." Names the core payoff plainly: one gauge setting serves both the mortise wall and the mating tenon cheek without ever resetting.
• Adam Cherubini, directly fetched [MOG17]. Prefers fixed-pin (non-adjustable) mortise gauges permanently dedicated to a single chisel, pins he shapes to a "half football" elliptical cross-section on gauges he makes himself to track cleanly with the grain rather than wander, a captured French wedge lock over a thumbscrew, and makes his own gauges from hardened cut nails — a working restatement of the Seaton-chest logic, three centuries later, from a named professional.
• Rob Cosman — referenced, not authored, by Derek Cohen: "Most novices try to emulate the lines cut by the likes of Rob Cosman in his DVDs, but lack his technique" [MOG17] — a named articulation of the beginner-trap below.

Forum voices — real disagreement, preserved rather than smoothed over, all directly fetched from three threads (Sawmill Creek "How many of you use a mortise gauge?" 2009; WoodCentral "I Need a Morticing Gauge, Which One?" 2007; Fine Woodworking "Mortise marking gauge?" 2008) [MOG16][MOG17][MOG20]:

• Robert Rozaieski argues the tool is misnamed — it should really be called a "tenon gauge," since the chisel, not the gauge, is what actually defines the mortise's width; the gauge only transfers that width.
• Mark Nowicki skips the mortise gauge entirely on principle: a single scribed line suffices once the chisel's own width is fixed and known.
• "wilbur" — a first-person beginner account: found the gauge itself hard to use accurately and switched back to pencil plus a single-pin gauge.
• Frank D. in Montreal counters that the real advantage isn't precision for its own sake but consistency: registering both the mortise and its mating tenon piece from the same reference face absorbs any variation in hand-planed stock thickness that a ruler-based approach would miss.
• Neal in San Jose — a genuinely useful, humbling finding: even a factory-fixed-width Tite-Mark cutter didn't match his actual chisels — "none of my mortice chisels are right on" nominal size. Directly supports the beginner-trap below (trusting a stamped or nominal width instead of the physical steel).
• SARGEgrinder47 — the entry's dangerous-misuse anchor (below): a first-person account of disabling the spare marking pin on his combination gauge with silicone glue and duct tape, because a leg stent and blood thinners made an exposed sharp spur on the bench a puncture concern he chose to engineer out. Kept as evidence that an exposed spare point concerned one user, not as a maintenance method: improvised adhesive or tape is not recommended. Use the maker's retraction, removal, cap or storage method, or a dedicated single-purpose gauge.

Trade home. The Marking Gauge entry's own museum record — Science Museum Group object 1949-336/11, a wheelwright's mortice gauge from R. A. Salaman's own collection (the Dictionary of Woodworking Tools author, the corpus's standing reference authority for the variations axis) [MOG21] — documents this exact twin-pin form in wheelwrighting, not only cabinetmaking; carried forward here rather than re-derived, since it is this tool's own object, not the plain marking gauge's.

✦ proof of existence

• Museum / collection record (HIGH): Science Museum Group, object 1949-336/11, "Wheelwright's mortice gauge" — wood and iron, 160×205×205mm, part of accession 1949-336, credited to R. A. Salaman's collection [MOG21]. Per the reviewer, the catalogue title supports trade association and physical existence; the text record by itself does not establish a twin-pin configuration or a date.
• Physical example (HIGH, as a documented example): the Seaton chest, Guildhall Museum, Rochester (1796) — the four-fixed-pin-set mortise gauge matched to Benjamin Seaton's own chisels, supplied by Christopher Gabriel & Sons, London, 1796, with a surviving invoice [MOG8]. Already cited in the parent entry; restated here as this tool's own strongest single physical anchor.
• Named-category text (HIGH): Nicholson, The Mechanic's Companion, 1812, §60 "The Mortice Gauge," verbatim, above.
• Patents (HIGH for the two directly fetched; MEDIUM-HIGH for the corrected third): GB-184,700,970 (Fenton & Marsden, a reported 1847 application or stamped patent reference with no surviving specification — dated only via stamped physical survivors, per Ken Roberts's Some 19th Century English Woodworking Tools, 1980, as cited by DATAMP) [MOG10]; US 132,421 (Traut/Stanley, 1872, brass gib + split-shaft) [MOG11]; and the corrected citation on US 36,973 (properly "Carpenter's Bench Gage," a general marking-gauge patent, not mortise-specific — flag for the parent entry) [MOG12].
• Currently manufactured, in traditional and modern forms (HIGH): as of the original run (July 2026), Crown Tools USA's category page listed dedicated mortise gauges — #154 with Screwslide, #153 Plated, #152 Rosewood — plus a miniature #152M and a combined #150 mortice-and-marking gauge, described as Sheffield-manufactured [MOG27]. Marples (marples.co.uk) confirmed rosewood mortice-gauge production in plain, brass-faced and brass-plated finishes [MOG23]. Lee Valley listed Standard and Deluxe mortise/marking gauges from Crown Tools [MOG24], and Veritas sells a dual marking gauge [MOG5]. Prices are not recorded here: The reviewer found on 2026-07-30 that the Crown page listed $95.95 (#154), $59.53 (#153) and $50.02 (#152) versus the original entry's figures, listed by Crown Tools USA on 2026-07-30 (USD), and that the Lee Valley prices were unchanged at review time [manual, relayed]. Prices vary by market, sale and date and are not evidence of anything about historical manufacture. Present production establishes present survival, not uninterrupted production.
• Honest gaps: no Smithsonian or Colonial Williamsburg object record was located this run (only general collection landing pages reached, not a specific accession) — an unexplored gap, not a checked negative. The Victoria & Albert Museum was not searched at all this run. Stanley No. 90/93/77 catalog dates rest on collector/dealer listings, not a primary Stanley catalog scan. A specific Marples 1873/1928 catalog claim and Preston Catalogue No. 18 (1909, confirmed digitized at archive.org but not opened this run) both remain unconfirmed follow-ups.

references

• [MOG1] Wikipedia, "Mortise gauge" — en.wikipedia.org/wiki/Mortise_gauge; confirms "Mortice gauge" as the standing UK alternate title. kind: encyclopedia
• [MOG2] Cross-check of UK manufacturer/retail spelling (Marples, Crown UK, Flinn-Garlick — consistently "mortice") against US retail (Lee Valley, Woodcraft, Rockler — consistently "mortise"). kind: retailer-doc (direct fetch, multiple)
• [MOG3] Sellers, "Mortise Gauges to Look For," paulsellers.com, 2017-02-18 — direct fetch. kind: blog/teaching-canon
• [MOG4] Taytools, "Wheel Marking Gauge Double Mortise Attachment Set" — taytools.com. kind: retailer-doc (direct fetch)
• [MOG5] Veritas Dual Marking Gauge product page — veritastools.ca/en-ca/shop/tools/hand-tools/marking-and-measuring/marking-gauges/67466-veritas-dual-marking-gauge; read directly 2026-10-16 (fix pass). Dodeca Gauge claim remains search-summary level. kind: maker-doc (direct fetch, fix pass)
• [MOG6] Nicholson, The Mechanic's Companion (1812), §60 "The Mortice Gauge" — verbatim text already retrieved and cited in the Marking Gauge entry [MG2]; restated here as this tool's own load-bearing anchor. kind: book/primary
• [MOG7] Holtzapffel, Turning and Mechanical Manipulation, Vol. 2 (1846), via Jansa [MG4] — already cited in the parent entry; restated here. kind: book/primary (secondary quotation)
• [MOG8] Rees (ed.), The Tool Chest of Benjamin Seaton, 1797 (TATHS); Jansa [MG4] — already cited in the parent entry as MG7; restated here as this tool's own physical anchor. kind: museum/book
• [MOG9] Follansbee, "Wedged Sliding Mortise Gauge," Popular Woodworking, 2022-10-07 — direct fetch. kind: magazine/blog
• [MOG10] DATAMP, GB-184,700,970 (Fenton & Marsden, 1847) — datamp.org/patents/displayPatent.php?id=82148; company lineage via Ken Roberts, Some 19th Century English Woodworking Tools (1980), as cited by DATAMP. kind: patent (direct fetch)
• [MOG11] DATAMP, US 132,421 (Traut/Stanley, 1872) — datamp.org/patents/displayPatent.php?pn=132421&id=34. kind: patent (direct fetch)
• [MOG12] DATAMP, US 36,973 — datamp.org; confirmed titled "Carpenter's Bench Gage," classified as a general marking-gauge patent, not mortise-specific (correction to the parent entry's MG9/MG10 citation). kind: patent (direct fetch)
• [MOG13] Google Patents, US 1,432,485, "Mortise gauge," Edward A. Moller, filed 1920, granted 1922 — full text, direct fetch. kind: patent
• [MOG14] DATAMP, "Butt and Mortise Gage" patents — US 432,328 (1890), US 985,504 (1911), US 1,197,308 (1916). kind: patent (direct fetch)
• [MOG15] Jansa, "Mystery of the Marking Gauge," Popular Woodworking, Dec 2006 — already cited in the parent entry as MG4; cited here for its independent forum-propagation record. kind: magazine
• [MOG16] Fine Woodworking forum, "Mortise marking gauge?" (2008) — direct fetch, named posters Neal, "wilbur," Rod Sheridan, joelm, Derek Cohen, SARGEgrinder47. kind: forum
• [MOG17] Sawmill Creek forum, "How many of you use a mortise gauge?" (2009) — direct fetch, named posters Derek Cohen, Adam Cherubini, Robert Rozaieski, Lataxe, Rob Cosman (referenced). kind: forum
• [MOG18] Collector/dealer listings, Stanley No. 90/93/77 — Jim Bode Tools, Worthpoint, eBay descriptions. kind: blog/collector (search-summary level, not primary-catalog-confirmed)
• [MOG19] Sellers, "Marking Gauges Part II — Mortise Gauges and More," paulsellers.com, 2014-06-20 — direct fetch. kind: blog/teaching-canon
• [MOG20] WoodCentral forum, "I Need a Morticing Gauge, Which One?" (2007) — direct fetch, named posters Dean J, Paul (NJ), MikeW, Frank D. kind: forum
• [MOG21] Science Museum Group, object 1949-336/11 — collection.sciencemuseumgroup.org.uk/objects/co45504; already cited in the parent entry as MG8, restated here as this tool's own object. kind: museum (direct fetch)
• [MOG22] Wikipedia, "Mortise gauge," anatomy section [MOG1]. kind: encyclopedia
• [MOG23] Marples Ltd, rosewood/beech mortice gauge listings — marples.co.uk/gauges/rosewood-gauges/, marples.co.uk/gauges/beech/. kind: maker-doc (direct fetch)
• [MOG24] Lee Valley, "Mortise/Marking Gauges" (Crown Tools, Sheffield), product #32621, Standard and Deluxe models (prices removed in the fix pass) — leevalley.com. kind: retailer-doc (direct fetch)
• [MOG25] Tools For Working Wood, "All About Marking and Mortise Gauges" — toolsforworkingwood.com/store/more/gaugeguide.html; already cited in the parent entry as MG25, restated for this tool's own mechanism description. kind: retailer-doc/teaching (direct fetch)
• [MOG26] Tools For Working Wood, same source as MOG25 — pin-height and end-splintering teaching notes. kind: retailer-doc/teaching (direct fetch)
• [MOG27] Crown Tools USA, marking/mortise/cutting gauge category page — crowntoolsusa.com/categories/marking-mortise-cutting-gauges; #154/#153/#152/#152M/#150 (prices removed in the fix pass; see proof of existence). kind: maker-doc (direct fetch, original run)
• [MOG28] Lee Valley, "Mortise and Tenon Work with the Veritas Dual Marking Gauge" — leevalley.com/en-us/discover/post-purchase/veritas-dual-marking-gauge/mortise-and-tenon-work-with-the-veritas-dual-marking-gauge; read directly 2026-10-16. Cutters work independently, one line at a time; setting changes between mortises and tenons so the bevels sit in the waste; shaft clamp allows fence repositioning with cutters aligned. The page itself gives no safety guidance. kind: retailer-doc/teaching (direct fetch, fix pass)
• [MOG29] CCOHS, "Working Safely with Sharp Blades or Edges" — ccohs.ca/oshanswers/safety_haz/sharp_blades.html; read directly 2026-10-16. Retraction after use, secure storage, stable work surface, mechanical workholding, avoid excessive pressure, keep body parts out of the cutting and slip path. kind: safety-authority (direct fetch, fix pass)
• [MOG30] CCOHS, "Hand Tools — General Hand Tool Operation" — ccohs.ca/oshanswers/safety_haz/hand_tools/general.html; read directly 2026-10-16. Inspect before use, cover sharp edges, do not hold work in the palm, store properly, eye protection, never cut toward the body. kind: safety-authority (direct fetch, fix pass)

forge images needed

• Anatomy callout — a classic wooden twin-pin mortise gauge shown beam-on (label it as one form; add a small inset of an independent-rod wheel gauge), with labeled parts: beam/stem, fence/stock, fixed pin, sliding pin, the internal brass rod, and the two separate thumbscrews (fence-lock vs. pin-slide adjuster) called out as functionally distinct controls. Pair with a small inset showing the "deluxe" threaded-rod mechanism beside the "standard" plain-post mechanism.
• Set-from-the-chisel, not the ruler — a two-panel teaching image: (left) the correct method, a mortise chisel presented to the two points to set their spacing, with fingers clear of the edge; (right) the beginner-trap version, a ruler or digital caliper reading a nominal number that doesn't match the actual chisel steel (Neal's own finding). Captions should make the entry's central discipline visually obvious at a glance.
• The naming-collision panel — three tools shown side by side at matched scale: a single-pin marking gauge, a twin-pin mortise gauge, and a triple-pin (2+1) combination gauge, captioned with Sellers's taxonomy sentence as one convention, and a note that retailers also sell the 2+1 tool as "mortise/marking gauge". Pin arrangement stated explicitly in the caption.

The reviewer's corrections (11)

• BLOCKER — Fix 1 — Exact claim: “Safety profile: thin/benign,” and “No general-population injury account was found ... [the medical-context anecdote is] the ceiling of documented danger for this tool.”
• BLOCKER — Fix 2 — Exact claim: “file the taller pin down to match, don't press harder to compensate,” plus “If they aren't, file one down slightly.”
• SHOULD-FIX — Fix 3 — Exact claim: “A marking gauge with two pins — one fixed, one sliding on an internal rod,” and the anatomy statements “Fixed pin — set permanently at the beam end” / “Sliding pin — mounted on an internal rod inside the beam.”
• SHOULD-FIX — Fix 4 — Exact claim: “used to scribe both walls of a mortise, or both cheeks of its mating tenon, from a single fence setting, so the joint's two halves are guaranteed to match,” and “a single pass per face.”
• SHOULD-FIX — Fix 5 — Exact claim: A plain marking gauge used twice carries “real added risk, since nothing enforces the two lines being parallel or exactly chisel-width apart.”
• SHOULD-FIX — Fix 6 — Exact claim: “Any joint that isn't a mortise or tenon” is a job the tool “should never do,” and machine-referenced joinery gives it “no operational role.”
• SHOULD-FIX — Fix 7 — Exact claim: “Not checking the setting is centered from both faces ... mark from each side and split the difference rather than trusting a single-face setting.”
• SHOULD-FIX — Fix 8 — Exact claim: “Set the pins from the actual chisel steel, never from a ruler or a nominal size.”
• SHOULD-FIX — Fix 9 — Exact claim: “the earliest well-documented physical solution,” “the earliest confirmed English mortise-gauge patent,” “direct sibling/descendant,” “the tool has never left production,” and the Jansa article “sent a generation of hobbyists” to reproduce the Seaton solution.
• MINOR — Fix 10 — Exact claim: Crown #154 at “$103.94,” #153 at “$66.06,” and #152 at “$55.47,” presented as “current pricing.”
• MINOR — Fix 11 — Exact claim: “a combination gauge — adds a third pin ... per the strict pin-count taxonomy,” and current “Mortise/Marking Gauge” listings are “technically” mislabeled.