# Wooden Folding Rule (Two-Foot Rule)

Hewn Tool Library · https://hewn.build/tools/wooden-folding-rule-two-foot-rule

Corrected: An independent reviewer read this entry and found corrections. They have been applied to the text, and the reviewer re-checked the correction that mattered most for safety and found it done; the others have not been re-checked yet. The list at the end is the record of what changed.

Cite as: "Wooden Folding Rule (Two-Foot Rule)." Hewn Tool Library, hewn.build/tools/wooden-folding-rule-two-foot-rule. Reviewed 2026-09-04.

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## Identity

- **Name:** Wooden Folding Rule, also **Two-Foot Rule** (a common trade name from the standard open length of the historical Anglo-American form), **Boxwood Rule**, **Carpenter's Rule**, **Box Rule**. The family also goes by **folding rule**, **jointed rule**, **zigzag rule**, **extension rule** and **folding metre stick**; these terms overlap, and patents and makers use them for variants of the same articulated family, so this entry does not force them into a clean ancestor and descendant line `[manual, relayed]`. When a rule carries a sliding brass arm for timber-volume calculation it is a **Coggeshall rule** or **carpenter's slide rule**; when it carries a caliper jaw it is a **caliper rule**. Not a duplicate of the already-built [[Tape Measure]] or [[Story Stick]] (both entries cite this tool by name without a file of their own).
- **Family/category:** A graduated linear measure made from rigid sections joined by pivots, compact when folded and straight, or angle-indexed on some models, when opened. Traditional Anglo-American examples include two-foot boxwood rules with brass joints or binding. Current forms commonly use beech or birch, composite, fiberglass-reinforced polymer, aluminum or metal, in nominal lengths such as 1 m, 2 m and 6 ft `[manual, relayed]`. The wooden two-foot, four-fold boxwood rule is an important **historical subtype**, not the universal form. Fold-count terms (twofold, fourfold, sixfold) follow the specific catalogue or object; no universal anatomy is inferred from one museum record.
- **One-line:** A graduated measure of rigid hinged sections that folds to a compact bundle and opens to a straight, self-supporting edge.
- **A directly catalogued museum anchor.** Science Museum Group (UK), object 1954-302, "Boxwood Coggeshall folding slide rule, 1720–1730": *"Boxwood Coggeshall rule, folding with slide, c. 1720-1730. Until the early 19th century slide rules were usually made for specific trades. This is a type of carpenter's rule."* Credited to the National Maritime Museum (Gabb Collection), maker unknown, closed dimensions 9 mm × 317 mm × 37 mm (read in the original run). It is evidence for one folding slide-rule form, not for the first hinged graduated rule (see History).

## How NOT to use it (the heaviest section)

**not-for**
- Energized electrical exposure. A wood, composite or fiberglass-reinforced folding rule is not rated insulation (see Matching).
- Following an arbitrary continuous curve with an ordinary model.
- Reading a board-rule volume table as the linear inch scale on the same rule (beginner-trap, below).

**dangerous**
The bare hand tool is low hazard. Its use context is not automatically low risk, and "low intrinsic hazard" is kept here only for ordinary hand measuring away from energized equipment and moving machinery.
- **Measuring or leaving the rule at a machine.** A measuring rule is commonly brought to saws and other machines, so measuring beside or leaving it on an active machine is a foreseeable hazard. OSHA's radial-saw machine guarding page directs users to use a stop gauge or turn the saw off when measuring by rule and to wait for the blade to stop; OSHA training material also says tools must not be placed on saw tables `[manual, relayed]`. Controls: stop the machine and wait until all motion has ceased before measuring or retrieving the rule; keep the rule off machine tables during operation; avoid reaching near the point of operation; follow the specific maker's warnings and workplace rules.
- **The table-saw account.** In the Sawmill Creek thread, Richard Jones says a Lufkin X46 got caught: "Table saw got hold of one once, not a pretty sight." The original run dismissed it as "a workshop-accident account, not a tool-specific danger." That dismissal is withdrawn. It is one unspecific first-person line, not a documented injury mechanism, but it matches the foreseeable machine-measuring hazard above, and the controls apply regardless of how that account is weighed.
- **Closing and snapping joints.** Hinged sections can pinch or snap shut. Keep fingers clear of closing joints when opening, folding and carrying.
- **Damaged rules.** Inspect sections, scales, joints, locks and extension slides before use. Cracked or loose tools that cannot hold alignment should be retired; damaged joints can invalidate readings.
- **Electrical exposure.** Do not rely on the rule's material for shock protection. De-energize and verify circuits where required.
- Manufacturer warnings and applicable workplace rules control.

**damaging**
- **Forcing the joint open by pulling the arms apart lengthwise rather than rotating them.** Sawmill Creek, "Have ever broken a folding carpenter's rule?" (2019), **Jack Frederick**: *"They break when you are careless, Pulling apart rather than rotating the sections open."* Others in the thread report breaking rules (**Osvaldo Cristo**, the articular joint of his father's and his own; **Tom Stenzel**, "number 3 now"), and several report never breaking one across decades (Kevin Hampshire, James Pallas). LeeLamb self-reports carelessness and skipped oiling. These are forum-level experiences. **The original run's verdict ("real, but user-error-dominated") is withdrawn.** US 1,829,975 addresses endwise shift and length error after pivot wear; it does not show wooden-arm breakage is user-error-dominated. Breakage causes are model-, material-, wear- and handling-dependent.
- **Non-straight grain in a boxwood arm** as a weak point, per **Mel Fulks** (same thread); one practitioner's statement, not an engineering finding. Fulks also says rules "are only accurate when completely UNFOLDED"; this is one forum poster's claim and, as Fix 2 of the review records, it is not a universal rule.
- **Worn joints and play.** Joint wear or play can cause length error; Witchger's patent describes up to 1/8-inch total variation in a worn eight-foot rule `[manual, relayed]`.

**beginner-trap**
- **Reading a rule whose numbering you have not confirmed.** Mel Fulks: misreading a fold line as an inch mark ruined a piece of walnut set aside for a client's lowboy top. The lesson is to confirm the face, direction and any extension reading before committing valuable stock.
- **Confusing a board/lumber rule's volume table with its linear scale.** Stanley's No. 82 and the "Lumber & Board Rule" category (EAIA's John Harkness collection of 35 named rules) carry both on one rule. No source narrates a specific misreading, so this is reasoned inference from the dual-scale design.
- **Treating a caliper or slide as a general-purpose inside, outside or diameter gauge** without the model's instructions.

**lineage-misuse**
- Assuming a folding rule can be flexed around a curve the way its relative, the steel tape, can.
- Treating the "beginning of the last century" claim (Tolpin, via [[Story Stick]]) as settled; see Lineage.
- Treating a company's "we invented the folding rule" story as the history of the generic tool.

## Correct use

**Genuinely good at.** Repeatable linear measurement across projects (unlike the one-off [[Story Stick]]); striking a crisp straight line directly off the rule's rigid edge; self-support over a span within the rule's stiffness; model-supported short and inside measurements; layout where the rule doubles as a straightedge.

**How to use it well.**
- Open by rotating each joint through its hinge rather than pulling the arms apart lengthwise. That pull-versus-rotate advice is forum-level care experience (Sawmill Creek, Jack Frederick); no manufacturer manual in hand confirms it. Follow the maker's instructions for the exact model.
- **Reading the scale:** use the correct face and graduation sequence for the particular rule. Keep the measuring section seated and aligned, and follow the model's inside-measure method. Some scales reverse at joints or require adding an extension reading, so confirm the numbering before committing valuable stock. The original draft's "read only when fully unfolded and flat" is withdrawn as a universal rule: Hultafors instructs users to fold the rule "to the required length," its Contact-Meter is designed to measure accurately when not completely unfolded, and historical extension-rule patents describe measurements with only one or two sections open `[manual, relayed]`. The single Sawmill Creek mishap (a fold line misread as an inch mark on walnut) is a caution about reading a model whose numbering you have not confirmed, not a ban on partial opening.
- Use the rule at machinery only under the controls in dangerous, below.

## Matching (the workbench's first read)

- **Does:** repeatable linear measurement on the scale of the exact model; a rigid straightedge for striking lines; self-support over short spans; model-dependent inside measurement, 90-degree indexing and special scales.
- **Suits:** layout where a crisp, pencil-flush line from a rigid edge matters more than reach; inside-corner and inside-cavity measurement where the model supports it; use as a complement to a tape. **Electrical work is not a match for this tool.** The original draft's "non-conductive rule near live electrical work" is removed: material alone does not make an ordinary rule an insulating or live-line tool. Klein's folding-rule catalogue warns "Never use on or near live electrical circuits," and OSHA requires energized-work tools to be designed, tested, intended, inspected and maintained for that duty `[manual, relayed]`. Circuits should be de-energized and guarded; only equipment specifically rated, tested and maintained for the electrical task may be relied on for insulation. A fiberglass-reinforced rule may resist moisture or carry less incidental metal (Hultafors says reduced metal content can help in electrical work), but that is not an energized-work rating `[manual, relayed]`.
- **Kit-fit — pairs with:** [[Story Stick]]; a marking knife or pencil; a [[Tape Measure]] as complement: tapes offer longer reach, compact retraction and curve conformity; folding rules offer rigid self-support and a stable marking edge `[manual, relayed]`. Accuracy depends on product class, condition, registration and technique.
  - **Substitutes for / is substituted by:** the tape has displaced the folding rule in much general trade use but has not eliminated it; practitioners across several trades report continued use for inside and layout work (forum-level).
- **Match by:** certified accuracy class, scale resolution, joint condition, reach, and operation. Recommended attributes: nominal length, section count, material, graduation system, accuracy class, joint lock angles, inside-measure method, extension or caliper type, special scale, and electrical rating (normally none) `[manual, relayed]`.
- **Conditional matches:** masonry modules, engineering tenths, board measure, blacksmith work, conduit angles and diameters need the exact specialist scale, material and geometry.
- **Not-for (project-keyed):** a standard folding rule does not conform continuously to an arbitrary curve the way a flexible tape does; distances beyond its capacity without a documented method; damaged or illegible rules; energized electrical exposure without purpose-rated protection; measuring on or beside moving machinery (see dangerous). The original "not for corners or any non-flat surface" is withdrawn: many articulated rules lock at 90 degrees, a 1897 patent forms inside and outside square corners, and modern special scales fold around a round object to read diameter `[manual, relayed]`. The original run supported that exclusion only by omission from its sources.
- **Access:** beginner-friendly for straight-line measurement; the skill gap is opening and closing technique and confirming the numbering of the exact model.
- **Revival:** a maker may pick this over a tape for the rigid edge and the flush strike, and because it is still made by named makers. A felt, reported accuracy advantage is practitioner anecdote; a rigid edge may improve placement for some users, which is not a claim that a folding rule is inherently more accurate than a tape.

## Anatomy

Named parts, from the Smithsonian's Stanley No. 32 object record and Lost Art Press: **arms/legs** (the rigid sections, commonly four on a "fourfold" rule), **joints/hinges** (the No. 32 carries "a brass arch joint at the center and two brass hinges"), **brass binding/caps** (edge protection; a collector marker: wooden scales "entirely bound in brass... less likely to have warped"), and the **graduated scale** (inches and sixteenths on one edge, twelfths or tenths on the other, on the No. 32). On the No. 32, a **brass caliper/slide** "slides out from the right end of the rule... divided to 1/16" and marked 1, 3/4, 1/2, 1/4." the reviewer cautions that the No. 32's scale layout must not be generalized to all caliper rules, and that the Smithsonian record describes the No. 32's construction but not all of the uses the original draft attributed to it `[manual, relayed]`.

**Joints vary by model.** A standard modern folding rule is articulated but its sections remain rigid. Some joints lock only at 180 degrees; others index at 90 and 180 degrees, or at 0, 90 and 180 degrees with angle-reference markings (Milwaukee's composite rule, per the reviewer) `[manual, relayed]`. Fully extended, a rule's straightness helps with spanning, self-support and marking, but joints add possible play and cumulative error: Hultafors states EU Class III tolerances of ±1.4 mm over 2 m and up to ±0.5 mm across an articulated joint `[manual, relayed]`.

## Variations (living)

Each variant has its own does, reading method and limits. Do not infer a variant's function from a slide or jaw without the model's instructions or a primary catalogue.

| Variant | What differs | Reading method and limits | Source |
|---|---|---|---|
| Plain folding rule (two-, four-, sixfold; wood, composite, fiberglass-reinforced, aluminum, metal) | Rigid sections on pivots; nominal lengths vary (two-foot historical; 1 m, 2 m, 6 ft current) | Linear measurement on the model's own scale; follow the model's lock angles | Science Museum Group; Smithsonian NMAH; the reviewer's relayed current-maker notes |
| Caliper / extension rule | An integral sliding jaw or extension (Stanley No. 32 documented) | Collector source describes classic caliper rules as measuring outside thickness; historical extension slides were often for inside dimensions. The reading may need a known body length added. Method is per model; not verified here for any particular rule | Smithsonian NMAH object nmah_904792; US 763,523 `[manual, relayed]` |
| Coggeshall / carpenter's slide rule | Sliding brass arm with a timber-volume calculation scale | The slide's material and scale come from the specific object | Science Museum object 1954-302; Smithsonian "Carpenter's Slide Rule by S. A. Jones," 1838–41 |
| Board/lumber rule | Volume-lookup tables (Doyle, Scribner, International ¼") | Volume tables are not the linear inch scale on the same rule | Adirondack Almanack; Stanley No. 82; EAIA |
| Trade-specialty rules (blacksmith's solid brass, mason's, tailor's, surveyor's, counter-measure) | Specialist scales; some solid brass, which is not a wooden rule | A related specialist rule, not a default capability of a wooden rule | Cherry; EAIA |
| Angle-indexing rule | Joints lock at 90 degrees in addition to 180 | Angle reference and inside-corner use per the model | Hultafors; Milwaukee `[manual, relayed]`; US 594,607 |
| Special diameter scales | Folding around a round object to read diameter | Per the model's scale | the review `[manual, relayed]` |
| Contact-Meter style | Short-measure rule designed to measure accurately when not completely unfolded, with reversed graduation | Reading direction reverses at the joint; per maker instructions | Hultafors `[manual, relayed]` |
| Zigzag / extension rule | Folds to a compact Z | Lufkin X-series still sold; named in patents as a folding rule | Lost Art Press-sourced material; US 1,829,975 |

## Trades (where it appears)

Carpentry and joinery (the most-repeated context); cabinetmaking (alongside the [[Story Stick]]); masonry (brick-spacing scale); surveying (fractional/100ths dual-scale form); engineering and machining (brass caliper-jaw rules, Smithsonian-documented); millwork; pipefitting and lineman work (forum corroboration); archaeological excavation (PureLeaf, Garage Journal); tailoring, hatting, drapery and millinery retail, and customs and excise work (Cherry's list, not independently corroborated). **Electrical work is not listed as a trade use.** The original "non-conductive fiberglass/wood rules near live circuits" is removed (see Matching and dangerous).

## Lineage

**Ancestors.** Straight, non-folding measuring rods and gauging rods. Joseph Moxon's *Mechanick Exercises* (begun 1677, published 1678) describes carpenters using a graduated two-foot rule ("divided into 24 equal parts") alongside a ten-foot rod for ground-plots; text located via Lost Art Press's hosted facsimile, not page-verified against the original printing. The **sliding** Coggeshall rule is a distinct documented form: Henry Coggeshall published *"A Treatise of Measuring by a Two-foot Rule, which slides to a Foot"* (1682, revised from an earlier 1677 work), a two-piece rule with one arm sliding in a groove in the other for timber-volume calculation, corroborated by a Computer History Museum record (catalog B170.81). The earliest physical folding example now cited here is older than either date; see History.

**Correction to a claim standing in this corpus.** [[Story Stick]]'s entry quotes (via Tolpin) an elderly cabinetmaker's claim that graduated rules "didn't even exist until the beginning of the last century." Museum-dated physical objects (the 1659 Assheton joint rule, the 1720–1730 Coggeshall rule) and the Moxon and Coggeshall texts show graduated rules in documented use centuries before 1900. The cabinetmaker may have been describing a shift in how common graduated rules became in ordinary practice around 1900; that is an inference, not a sourced finding. [[Story Stick]] should be light-touched to note the correction.

**Descendants and relatives.** The steel pocket tape measure is a related later measure. Per Lost Art Press's "Two-Foot Rules" (mixed fetch record in the original run, held at MODERATE confidence), tape measures existed earlier in isolated patented forms but "didn't become ubiquitous... until the 1930s or so," consistent with Stanley's tape-measure ramp-up from the late 1920s (John Walter, *Stanley Tools*, cited secondhand). This is a trade-blog and secondhand-book claim about ubiquity, not a measured market record. **Multi-section zigzag rules are not simply a twentieth-century descendant:** current patents call the articulated multi-section object a folding rule, and the 1931 Witchger patent already treats "zigzag rule" as the relevant category `[manual, relayed]`. Lufkin's X-series (X46, X46F, X48N) remains a named zigzag family still sold. No dated record was found for when the name "zigzag" entered trade use.

**Contemporaries.** [[Story Stick]], a non-graduated, project-specific reference tool that coexisted with the folding rule (cross-referenced from [[Story Stick]]'s own entry, not re-derived). The **board/lumber rule** (Doyle 1825, Scribner 1846, International ¼" 1906 scaling tables) is a related specialist rule carrying volume-lookup tables, sometimes built onto a folding-rule-like stick (Stanley No. 82 carried interior board-foot tables). It is not a wooden folding rule's default capability set.

## History (Petroski "form follows failure" lens)

**Documented physical record, in date order.**
- **1659.** The Science Museum Group catalogues Richard Assheton's signed, two-foot pearwood "Carpenter's joint rule," folding to about 12 1/2 inches and carrying multiple graduated trade scales [SMG-1659] `[manual, relayed]`. This is the earliest physical folding graduated rule cited in this entry, and it precedes the 1677–82 and 1720–1730 dates the original draft used to frame the origin. The original draft's "origin" headline is withdrawn: "origin" is not claimed unless the search is exhaustive, and it is not.
- **1677–82.** Coggeshall's sliding two-foot rule is documented in print (see Lineage), a published sliding system rather than a hinged one.
- **1720–1730.** The Science Museum Group's Boxwood Coggeshall folding slide rule (object 1954-302), a later documented folding form with a slide [SMG-1954].

**Company origin stories are claims about particular modern forms, not the generic tool.** STABILA says the Ullrich brothers invented the folding rule in 1865 and later patented a spring-loaded joint; Hultafors says Karl-Hilmer Johansson Kollén constructed the folding rule in 1883. The two statements are incompatible with each other and with the older museum objects above `[manual, relayed]`. They can support their own company and product histories, not the invention of the tool. A dealer source (Old Woodworking Tools) that says folding rules were "first invented in Germany in the early 1800s" is contradicted by the older objects and not repeated.

**The failure the hinge solves, read against Petroski's lens.** A straight rigid rod of useful trade length is awkward to carry; a hinged rule keeps rigidity when open and compacts when closed. A rigid tool that folds carries a structural weak point at the joint, and the joint-hardware patents below record manufacturers working on joint alignment, play, spring action and length accuracy. That reading is Haft's inference from the patent trail, offered as a lens and not a causal proof of why any particular rule fails.

**Named manufacturers (directly documented dates only).** Stanley Rule & Level Co. (New Britain, CT) made folding rules "almost since the company's inception in 1843" (Walter, via the Smithsonian's object record). Its No. 32 (four-fold boxwood, brass arch joint, integral caliper) was offered 1859–1941 and the particular Smithsonian object is dated ca. 1892; its No. 62 (four-fold, 2-ft, brass-bound) ran 1855–1942. The Smithsonian record supports those No. 32 model and object dates, not Stanley-wide inception claims unless separately sourced `[manual, relayed]`. John Rabone & Sons (Birmingham, founded by Michael Rabone 1784, so named 1877, merged with James Chesterman & Co. in 1963, acquired by Stanley 1989) rests on Graces Guide, a UK industrial-history wiki: reliable for corporate dates, not peer-reviewed. Lufkin Rule Co. (Saginaw, MI, 1869) entered the carpenter's boxwood folding-rule market "shortly after WWI," per a Crafts of NJ collector-association article, held at MODERATE confidence. Manufacturer chronologies here rest on trade blogs, collector sources and company marketing and are not independently verified.

**Two patents, read in the original run, on the joint.** US 1,069,186, "Folding Rule," Frank X. Rudler (Buffalo, NY), assignor to James H. McCaffrey, filed April 7, 1911, granted Aug. 5, 1913: a stamped spring-tongue/slot joint plate intended to be "light, strong, neat and compact," locking the sections both open and folded. US 1,829,975, "Joint for Folding Rules," Eugene J. Witchger, assigned to Lufkin Rule Co., applied Dec. 9, 1929, granted Nov. 3, 1931 (via DATAMP): per the reviewer, the patent addresses endwise shift and length error after pivot wear; its latch prevents overlapping sections moving longitudinally. **It does not investigate wooden-arm fracture, quantify user fault, or establish that pulling sections apart is the dominant cause of breakage**, and this entry uses it only as evidence that joint play and length accuracy were recurring engineering concerns. Witchger's patent says worn joints in an eight-foot rule could create up to 1/8-inch total variation `[manual, relayed]`. Further patents bear on method: US 763,523 documents measuring with only selected sections unfolded and an extension/caliper section, and US 594,607 supports a folding rule deliberately used at right angles for inside and outside square corners `[manual, relayed]`. Two other joint patents (US 1,847,757, 1932; US 2,713,206, 1955) were located but not read, and are unverified leads.

## Human Side

**Traditions and trades.** Dan Cherry's "Collector's Guide to Rules" (Woodworkers Institute) states specialized folding rules were made for "tailors, coopers, engineers, surveyors, farmers, hatters, ironmongers, architects, military, navigation and even the customs and excise branch of government," each often carrying trade-specific, non-standardized scales. These are specialist variants with their own scales, not default capabilities of a wooden rule. Named forms, as sourced: blacksmith's rules of solid brass "to avoid scorching in a highly heat-infused workspace" (Rabone No. 1243); mason's brick-spacing rules (three named forum posters); "counter measure" rules for drapery and millinery shops (Ted Hopkins, EAIA); a six-foot baggage-measuring caliper rule by Kerby & Bros. of NYC (est. 1847, closed 1953) used aboard the *S.S. Roosevelt* (Brian Lants, EAIA). Regional pre-metric inch units appear (Paris *pouce*, Rhineland *zoll*, Spanish *castile*, Danish *tomme*; Cherry).

**Named voices on real use (forum-level, practitioner anecdote).** Garage Journal, "What do people use folding rules for?" (2021): **HenryAZ** (25 years in a millwork shop) — *"I used a folder (usually Lufkin) when working in a millwork shop for 25 years. All of us did... My work pants typically wore out the right rear pocket first."* **quattro_sinko** — *"if you want to reliably measure to the 32nd (or better) a folding rule is the only way to go."* That last line is a practitioner's preference, not instrument-comparison evidence, and is not carried as a finding. Trade corroboration in the same thread: masons (**astroracer**, **Renegade1LI**), surveyors (**Renegade1LI**), linemen and pipefitters (**mark#3**, **dr_clyde**), and archaeological excavation (**PureLeaf**). **neophyte** reports using fiberglass or wood rules near live circuits: this is one forum poster's practice, and it is not endorsed here; see dangerous. Fine Homebuilding forum, "Broke my folding rule today" (LeeLamb, 2008): a six-foot Stanley owned since 1967 finally breaks at the second joint; his daughter Kate later swaps her worn Lufkin for his. **Jay20**, same thread, 15 years of folding-rule use before ever buying a tape: *"when looking for accuracy I always revert to mine."*

**A named practitioner on why a rigid edge helps.** Jay20: with a tape, "you have to align your pencil against the relevant mark... whereas with a folding rule you can align the mark accurately with the butt of the material and strike a crisp, straight line off the end of the rule." Garage Journal posters (quattro_sinko, HenryAZ, RTM, Git, jsaw) corroborate use for inside measurement and layout on a stick. A German-tradesman preference for folding rules over tapes recurs in the same thread (dnschmidt, quattro_sinko, RTM); forum anecdote only. No engineering source here quantifies tape-blade sag at the 1/16"–1/32" level.

**Current production, scoped.** Skowhegan Wooden Rule Co. (North Anson, Maine), descended from E.T. Lufkin's 1869 board-and-log-rule company, wood operations in Maine by the mid-1960s, purchased by the Meisner family in 1999, still producing flatwood rules (company "About Us" page, original run). STABILA and Hultafors each sell wooden folding rules today (STABILA current beech construction and joint engineering `[manual, relayed]`; Lee Valley's current 2 m birch and steel rule with detents `[manual, relayed]`). This shows current manufacture by named makers; it is not a record of uninterrupted production.

## Proof of existence

- **1659 Assheton joint rule.** Science Museum Group, a signed, two-foot pearwood carpenter's joint rule, folding, with multiple graduated trade scales [SMG-1659] `[manual, relayed]`. The earliest physical folding graduated rule cited here.
- **1720–1730 Coggeshall folding slide rule.** Science Museum Group object 1954-302, boxwood and brass, closed 9 mm × 317 mm × 37 mm, credited to the National Maritime Museum's Gabb Collection, maker unknown [SMG-1954]. It does not establish origin or category-wide dominance.
- **Fourfold boxwood rule.** Science Museum object 1921-165 by J.H. Adams of Liverpool (3 ft long, brass and boxwood, folded 24 × 3.1 cm) corroborates the fourfold trade category [SMG-1921].
- **Smithsonian NMAH, "Stanley Folding Rule with Caliper,"** object ID 1990.0099.01, ca. 1892 (dated via the caliper-jaw shape, per Philip E. Stanley's *Boxwood & Ivory*, cited in the museum record), boxwood and brass, transferred from the Smithsonian's Department of Entomology, where it was used to measure insect specimens [SI-NMAH]. The record supports the object's four-fold construction, brass joints and slide, graduations and dates.
- **Patents:** US 1,069,186 and US 1,829,975, on joint design and length accuracy (see History); US 763,523 and US 594,607 for partial-section and right-angle use `[manual, relayed]`.
- **Commercial record, bounded.** Examples exist from the 1720s object forward; named makers are documented in the 19th and 20th centuries; and Skowhegan, STABILA and Hultafors sell wooden folding rules today. The object records prove examples existed. They do not prove dominance, and the entry makes no claim of uninterrupted production across three centuries: continuous production would need manufacturer-specific records. The accurate summary is "widely produced and used in documented European and North American trades."

## References

Kinds are distinguished: museum records, patents, manufacturer instructions, trade histories, collector material and forum anecdotes. Where the original entry gives only a host and an exact URL is not at hand, that is stated. No page was re-fetched in this pass, so no access dates are given.

| Tag | Title | Author/Source | URL | Kind | Notes |
|---|---|---|---|---|---|
| SMG-1659 | Carpenter's joint rule (1659), Richard Assheton | Science Museum Group | collection.sciencemuseumgroup.org.uk/objects/co60494/carpenters-joint-rule | museum object record | `[manual, relayed]`, not read by me |
| SMG-1954 | Boxwood Coggeshall folding slide rule, 1720–1730 (object 1954-302) | Science Museum Group | collection.sciencemuseumgroup.org.uk/objects/co60485/boxwood-coggeshall-folding-slide-rule-1720-1730 | museum object record | read in the original run |
| SMG-1921 | Fourfold boxwood rule (object 1921-165), J.H. Adams of Liverpool | Science Museum Group | collection.sciencemuseumgroup.org.uk/objects/co59264 | museum object record | original run |
| SI-NMAH | Stanley Folding Rule with Caliper (1990.0099.01) | Smithsonian NMAH | americanhistory.si.edu/collections/object/nmah_904792 | federal museum record | original run; cites Philip E. Stanley's *Boxwood & Ivory* |
| LAP | "Two-Foot Rules" | Lost Art Press | blog.lostartpress.com/2017/04/27/two-foot-rules/ | trade blog, quoting *The Joiner and Cabinet Maker* | mixed fetch record in the original run; MODERATE; supports ubiquity claims only as blog-level |
| US1069186 | US 1,069,186, "Folding Rule," F.X. Rudler (1913) | Google Patents | patents.google.com/patent/US1069186A | patent | original run |
| US1829975 | US 1,829,975, "Joint for Folding Rules," E.J. Witchger (1931) | Google Patents (the reviewer); DATAMP | patents.google.com/patent/US1829975A/en; datamp.org/patents/displayPatent.php?pn=1829975&id=13018 | patent | supports joint play and length error only |
| US763523 | US 763,523, "Measuring-rule" | Google Patents | patents.google.com/patent/US763523A | patent | `[manual, relayed]` |
| US594607 | US 594,607, "Folding ruler" | Google Patents | patents.google.com/patent/US594607 | patent | `[manual, relayed]` |
| SC | "Have ever broken a folding carpenter's rule?" | Sawmill Creek forum (Jack Frederick, Osvaldo Cristo, Tom Stenzel, Richard Jones, Mel Fulks, Kevin Hampshire, James Pallas; 2019) | sawmillcreek.org/threads/have-ever-broken-a-folding-carpenters-rule.272832/ | forum anecdote | original run |
| FHB | "Broke my folding rule today" | Fine Homebuilding forum (LeeLamb, Jay20; 2008) | finehomebuilding.com/forum/broke-my-folding-rule-today | forum anecdote | original run |
| GJ | "What do people use folding rules for?" | Garage Journal forum (2021) | garagejournal.com/forum/threads/what-do-people-use-folding-rules-for.474977/ | forum anecdote | original run |
| CHERRY | "Collector's Guide to Rules" | Dan Cherry, Woodworkers Institute | woodworkersinstitute.com/collectors-guide-to-rules/ | collector guide | original run |
| EAIA | "Rule Collectors' Rule" | EAIA | eaia.us/post/rule-collectors-rule | collector-association article | original run |
| SKOW | Skowhegan Wooden Rule Co., "About Us" | company | skowheganwoodenrule.com/about-us/ | company history page | current-production continuity only |
| GRACE | Rabone Chesterman; John Rabone and Sons | Graces Guide | gracesguide.co.uk (host only in the original; exact page URL not recovered) | UK industrial-history wiki | MODERATE; corporate dates |
| CNJ | "The Lufkin Rule Company Takes on Stanley" | Crafts of NJ | craftsofnj.org/tool-shed (host path only in the original; exact page URL not recovered) | collector-association article | MODERATE |
| MOXON | *Mechanick Exercises* (1677–78) | Joseph Moxon, via Lost Art Press facsimile | blog.lostartpress.com/2013/05/13/free-download-joseph-moxons-mechanick-exercises/ | primary-source facsimile host | not page-verified |
| COGG | Coggeshall slide rule | Wikipedia; Computer History Museum (B170.81) | en.wikipedia.org/wiki/Coggeshall_slide_rule; computerhistory.org/collections/catalog/B170.81 | encyclopedia and museum record | the museum record corroborates the summary |
| HULT1 | Folding rules—Developed with expertise | Hultafors | hultafors.us/articles/folding-rules-developed-with-expertise | manufacturer instructions | `[manual, relayed]`; fold to required length; Class III tolerances |
| HULT2 | Contact-Meter | Hultafors | hultafors.us/articles/contact-meter-a-folding-rule-that-stays-flat-on-the-surface | manufacturer page | `[manual, relayed]`; not an energized-circuit rating |
| MILW | Composite Folding Rule | Milwaukee | milwaukeetool.com/products/details/composite-folding-rule/48-22-3801 | manufacturer page | `[manual, relayed]`; 0, 90, 180-degree joints |
| KLEIN | Measuring tools catalogue | Klein Tools | data.kleintools.com/sites/kleintools/files/tool-catalog/10-Levels-MeasuringTapes-Catalog.pdf | manufacturer catalogue | `[manual, relayed]`; "Never use on or near live electrical circuits" |
| OSHA269 | 29 CFR 1910.269 | OSHA | osha.gov/laws-regs/regulations/standardnumber/1910/1910.269 | regulation | `[manual, relayed]`; live-line tools must be designed, tested and maintained |
| OSHARS | Machine Guarding—Radial Saws | OSHA | osha.gov/etools/machine-guarding/saws/radial | regulator guidance | `[manual, relayed]`; turn the saw off and wait for the blade to stop when measuring by rule |
| STAB | Quality and technology of folding rules | STABILA | stabila.com/en-US/products-553/quality-and-technology/folding-rules.html | manufacturer marketing | `[manual, relayed]`; company origin narrative not used as generic history |
| LV | Lee Valley Wooden Folding Rule | Lee Valley | leevalley.com/en-gb/shop/tools/hand-tools/marking-and-measuring/rules/72486-lee-valley-wooden-folding-rule?item=99W8693 | retailer page | `[manual, relayed]`; does not establish accuracy over tape |
| INT | [[Tape Measure]], [[Story Stick]] | Haft corpus | internal sibling entries | internal | grounding and cross-citation |

## The reviewer's corrections (11)

- `BLOCKER` — 1. — Exact claim: “site/trade work where a non-conductive (wood/fiberglass) rule is preferred near live electrical work,” repeated under Trades as “non-conductive fiberglass/wood rules near live circuits.”
- `BLOCKER` — 2. — Exact claim: “Read the scale only when the rule is fully unfolded and flat,” and “The rule’s own scale is only trustworthy fully open and flat.”
- `SHOULD-FIX` — 3. — Exact claim: The “Origin” section identifies the sliding rule in 1677–82 and the hinged, folding, graduated form in 1720–1730.
- `SHOULD-FIX` — 4. — Exact claim: “A rigid, brass-hinged boxwood rule” of two feet is presented as the family’s one-line identity, while the “20th-century” zigzag/extension rule is treated as a descendant.
- `SHOULD-FIX` — 5. — Exact claim: A folding rule is “the only way” to measure reliably to 1/32 inch or better; users choose it “for the precision”; the entry repeatedly frames it as more accurate than a tape.
- `SHOULD-FIX` — 6. — Exact claim: US 1,829,975 confirms the “identical failure mode” named by a forum poster and proves hinge breakage is “real, but user-error-dominated.”
- `SHOULD-FIX` — 7. — Exact claim: “Not-for: measuring around a curve, corner, or any non-flat surface,” supported because curved use cases were absent from the checked sources.
- `SHOULD-FIX` — 8. — Exact claim: Caliper models provide “direct inside/diameter measurement,” Coggeshall models use a “sliding brass arm,” and board, blacksmith, mason, tailor, surveyor, and other rules are treated as living variations of one capability set.
- `BLOCKER` — 9. — Exact claim: The Dangerous section treats the table-saw incident as merely “a workshop-accident account, not a tool-specific danger” and otherwise stops at an injury-search gap.
- `SHOULD-FIX` — 10. — Exact claim: “the dominant Western trade measuring tool for roughly two centuries,” tape ubiquity “until the 1930s or so,” “continuous…unbroken” three-century production, and multiple company/model chronologies.
- `SHOULD-FIX` — 11. — Exact claim: References use host-only or ambiguous values such as `gracesguide.co.uk`, `craftsofnj.org/tool-shed`, and `this corpus`; provenance repeatedly reports “research pass,” “search-synthesis,” and “Hewn” verification.