# Framing Square Hewn Tool Library · https://hewn.build/tools/framing-square 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: "Framing Square." Hewn Tool Library, hewn.build/tools/framing-square. Reviewed 2026-07-29. --- ## identity **Name:** Framing square (also carpenter's square, steel square; sometimes rafter square — see *lineage-misuse*). **Alternate names:** "steel square" is the traditional trade and book-title term (Hodgson, *The Carpenters' Steel Square and Its Uses*, 1880; Siegele, *The Steel Square*, 1981). "Framing square," "carpenter square" and "rafter square" overlap in current catalogs and the names are ambiguous across brands: some makers (Swanson, Stanley) use "rafter square" for this large L, others (Empire, Irwin) for the small triangular [[Speed Square]]; Home Depot files the L under "Carpenter Squares" [FS14][FS26][FS28][FS32][FS33][FS34][FS35]. **Family / category:** Layout and marking tools → fixed-angle reference squares, large-format/jobsite branch. **One line (review fix 5):** A flat L-shaped measuring and layout tool with a wider body or blade and a narrower tongue meeting at the heel. Common full-size construction models are about 16 × 24 inches and may carry fixed rafter, brace, octagon and board-measure tables. These tables make selected layout relationships available without fresh calculation; they are not a slide rule (which uses sliding logarithmic scales — Smithsonian NMAH slide-rule collections [FS38]) and not a complete trigonometric system. The two arms form a right angle in one plane; a modern one-piece square is cut, blanked, stamped, cast or machined as a flat L, not bent. --- ## ✦ how NOT to use it ### Not-for - **Proving a large assembly square from one corner** — Sellers: checking a large frame's corner with "a speed square or even a larger framing square... could possibly be a quick check... but overall it is not a good way of testing for square at all"; compare diagonals [FS19]. - **Precision joinery beyond the square's verified tolerance** [FS5]. - **Hand-held circular-saw guide** — see *dangerous*. ### Dangerous *(the holding finding rebuilt — review fixes 1, 10)* The square is passive and has no moving parts; the risk follows the operation. Not locating an injury report about a framing square is a research result, not evidence that matched procedures are safe. **Intrinsic to the tool** - Sharp burrs and damaged metal edges can cut hands — inspect and deburr or retire. - A large metal square can fall or create a trip or handling hazard — store it flat or hung, not on the floor or at height. **From matched operations** - **Circular saw.** A loose or unsuitable guide can contribute to loss of control, blade binding or kickback. The flat framing square has **no hooked lip** — the "hook and run the saw" technique belongs to the Speed Square (This Old House) [FS22] and must not be transferred. Only a verified-straight square, **clamped** clear of motor, guard and cut path, with the work fully supported and secured, base-to-blade offset verified and a dry clearance run, per the saw manufacturer's instructions [FS40]. - **Roof and stair layout** — incorrect layout can cause falls (a stair with bad rise/run), failed fit, or structural defects. Treat it as consequential technical work: approved plans, applicable code, the square's instructions, and a test-fitted first piece. - **Elevated and power-tool work** carries the controls of those operations (fall protection, saw PPE) even though the square has none of its own. ### Damaging - **Wet storage** — steel squares rust and become hard to read; aluminum can oxidize or corrode. Keep clean and dry; a light coat of paste wax or oil on steel; store flat or hung [FS21][FS29] (forum content at reduced confidence). - **Drops and impact — the invisible failure.** A struck square can go silently out of true at the heel. Toomey: "A square that has been dropped on concrete, cooked on a dashboard, or worn round at the fence will happily mark all day, wrong" [FS18]. - **Correction (review fix 4).** If the flip test shows disagreement, **remove the square from precision layout service.** Clean and inspect the heel and edges, repeat the test on a verified straight reference, and follow the manufacturer's inspection, warranty or replacement guidance. Traditional punch-truing is an advanced, material-specific practice and is not recommended as a general field repair; it can worsen aluminum, stainless, coated, hardened or precision squares and obscure heel damage. Any corrected square must be independently reverified before use. (The former hammer/center-punch instructions are withdrawn.) - **Prying or levering** with the square — bends the arms and ruins the heel [FS29]. ### Beginner-trap - **Applying a ridge correction the wrong way or along the wrong line (review fix 2).** Osborne and Toomey both name missing the ridge correction as a common error that makes every rafter long [FS17][FS18]; the fix is not one universal subtraction but following the square's method for where the correction applies, then test-fitting the pattern rafter. - **Reading the wrong row or face** — reported in a search summary only [FS31]; the practical guard is reading the legends on your own square. - **Registering off a damaged stock edge, or drifting on the flip** — Toomey [FS18]. - **A thick pencil line** eating the tolerance — Toomey says nearly 1/4" [FS18]. - **Trusting an unverified square** — flip-test before layout [FS22]. ### Lineage-misuse - **"Rafter square" names two different tools.** Empire and Irwin use it for the small triangle; Swanson for its 16"×24" aluminum L (TA122/TA127); Stanley's support page: "A rafter square, or more commonly called a framing square, is an L shaped square 16 inches on the short side and 24 inches on the long with rafter tables printed on it"; Home Depot files the L under "Carpenter Squares" [FS28][FS32][FS33][FS34][FS35]. A matcher must identify the shape, not the name. - **Transferring Speed Square instructions to the flat L** — above all the lipped saw-guide technique (review fix 1). - **Using a precision workshop square as a jobsite tool, or a construction square for shop-critical joinery** [FS5]. --- ## correct use *(brief — the workbench holds deep operation)* - **Verify the square first — the flip test.** Scribe along one edge, flip the square on the same straight reference edge, scribe again; if the lines "make a narrow X or V, it's off" [FS22][FS30]. A square that fails leaves precision layout service (see *damaging*). - **Reading the rafter table (review fix 2).** Use the instructions supplied for the square and the project's approved roof layout. Identify whether the table assumes total span or one-half run and where the ridge correction is applied — some methods deduct ridge thickness from the building width before calculating, some locate a deduction at the top plumb cut, some describe a half-thickness adjustment associated with one rafter (Swanson and Johnson instructions) [FS39][FS23]. Do not apply a dimension along a line other than the one the method specifies. **Mark and test-fit the first pattern rafter — including the ridge and seat-cut references — before transferring it to the remaining stock** (Haun's "make one, copy it"; Osborne's "PAT") [FS16][FS17]. - **Stepping off** rafter length in run increments — a table-free alternative [FS17]; same test-fit rule. - **Stair gauges** — clamp at the rise/run marks and repeat down the stringer [FS15]; the stair's rise, run and headroom come from the plan and the code, not the square. - **Local corners vs whole assemblies (review fix 9).** Use the square to establish or inspect a local 90° corner. For a large rectangular frame or opening, verify the whole assembly by comparing diagonals and checking straightness, level, plumb and the specified dimensions. A good local corner does not by itself prove the assembly is square [FS19]. - **As a straightedge for a circular saw (review fix 1).** A verified-straight framing square may sometimes serve as a **clamped** straightedge for a short circular-saw cut, but it has no hooked fence. Follow the saw manufacturer's instructions; fully support and secure the work; use an approved guide or a rigid straightedge securely clamped clear of the motor, guard and cut path; verify the base-to-blade offset; and make a dry clearance check before starting. **Do not hand-hold a loose framing square as the only guide** (Bosch and Makita circular-saw manuals on clamping, support, clamp clearance, binding and kickback [FS40]). --- ## ✦ matching *the workbench's first read — the passive tool is modelled separately from the operation performed with it* - **does:** marks long straight and perpendicular lines across wide stock; establishes or checks a local 90° corner; where tables are present, gives rafter, brace, octagon and board-measure relationships; with stair gauges, repeats stringer rise/run marks; lays out rafter plumb, seat and bird's-mouth marks per the square's instructions; can serve as a clamped straightedge for a short saw cut (conditions under *correct use*). - **suits:** roof and stair layout, deck/floor/wall framing layout, large-timber and sheet-goods marking. - **tables are optional capabilities** — detect from the actual model; do not assume. - **kit-fit:** *pairs with* stair gauges; a speed square for quick one-handed marking; the square's instructions, a rafter-table book or a construction calculator for cross-checking. *Global rectangularity* is matched to diagonal comparison plus straightness, dimension, level and plumb — not to the square alone. *Cannot replace* the lipped fence of a speed square (a different tool) [FS22], and is not a substitute for a precision square where the job's tolerance is tighter than the square is verified to [FS5]. - **not-for (tolerance-based, review fix 9):** precision joinery whose tolerance is finer than the particular square is verified to hold; proving a large assembly square by a single corner check. An accurate framing square can serve some workshop layout tasks. - **access (review fix 3) — set per operation:** - **Beginner:** identify the tool, read ordinary graduations, mark straight lines, check a small/local corner after verifying the square with the flip test. *"Beginner-safe" applies only to passive marking and local checking, not to every task in this entry.* - **Guided / intermediate:** stair gauges, repeated stepping-off, table interpretation, large-assembly layout checks. - **Advanced or plan-controlled:** roof and stair geometry, structural layout, correction/truing, and any power-tool guide use. - **revival (review fix 11):** plain and table-bearing squares are in current production. Precision workshop squares are modern tools using the framing-square form; their marketing supports their tolerance claims, not a lineage or a broad revival. Calculators and apps are alternative workflows alongside the tables. --- ## anatomy *Common pattern; table location, numbering direction, graduation system and even table presence are model-specific — read the legends stamped on your square (review fix 6).* - **Body / blade** — the longer, wider arm; on common full-size models 24" × 2". Johnson Level's instructions place the rafter tables on the face and the Essex board-measure table on the back [FS23]. - **Tongue** — the shorter, narrower arm; commonly 16" × 1½"; octagon scale on the face and brace table on the back on Johnson's layout [FS23]. - **Heel** — the outside corner; often the maker's stamp. Inspect it for damage. - **Rafter tables** — where present: length-per-foot-of-run for common, hip, valley and jack rafters at a range of pitches, with cut references. Which run convention (total span vs one-half run) and where the ridge correction applies depend on the maker's instructions (see *correct use*) [FS23][FS39]. - **Brace table**, **octagon scale**, **Essex board measure** — where present [FS23][FS24]. The Essex table is described as found on some older blades but "not on most modern framing squares" [FS11]. - **Graduations** — 1/8, 1/10, 1/12 and 1/16 divisions across edges on current specs (Johnson CS9; Irwin steel and aluminum) [FS23][FS25][FS26]. - **No fence or lip.** The flat L has nothing to hook over a board edge (review fix 1) [FS22]. --- ## variations | Variant | What differs | What it's for | |---|---|---| | **Steel framing square** | Stamped or coated carbon steel, commonly 16"×24" | Traditional jobsite form; heavier; rusts if stored wet [FS27] | | **Aluminum framing square** | Anodized aluminum, laser-etched or stamped | Lighter carry. **Does not develop iron rust but can oxidize or corrode** (review fix 6) [FS27] | | **Stainless framing square** | e.g. Johnson CS9 (1/8" thick) | Corrosion resistance; its own care and damage profile [FS25] | | **Black anodized square** | Finish feature, not a mechanical type (Swanson) | Contrast and reduced glare under some conditions [FS28] | | **Metric square** | e.g. Empire 1140M, 400 × 600 mm | Metric jobs [FS27] | | **Smaller carpenter squares** | Less than full size, table sets vary | Smaller layout work (review fix 6) | | **Precision workshop squares using the framing-square form** | Machined/ground, maker-stated tolerance, no rafter tables (Woodpeckers) | Panel and setup squaring at shop tolerance [FS5] | | **Small triangular "rafter square"** | A different tool — the [[Speed Square]] | Not a variant, despite the shared name on some sites | --- ## trades - **Carpentry / roof framing** — the home trade of the table-bearing square. - **Stair building** — with stair gauges. - **Deck and general framing** — local layout and brace layout; global squareness by diagonals. - **Woodworking** — tolerance-dependent: some layout tasks yes; precision joinery to a smaller or tighter-specified square. --- ## lineage **Predecessor family (review fix 8)** - **Try squares** — the [[Try Square]] entry's record (Egyptian, Roman, Moxon 1678) documents the older family of fixed right-angle squares. That is a functional precursor and shared purpose, not a documented line of descent into the table-stamped steel square. - **Earlier evidence of iron squares.** The University of Vermont finding aid for the Eagle Square Manufacturing Company Records cites Paul B. Kebabian, *American Woodworking Tools* (1978, p. 188): "steel squares were known at least two hundred years earlier" — an iron square belonged to Francis Eaton at Plymouth Plantation, and two iron squares were listed among the tools of Governor Theophilus Eaton of New Haven at his death in 1657 [FS1]. This shows Hawes did not invent the metal square; it does not by itself establish a manufacturing or design lineage into Eagle's table-stamped form. **The founding story — legend, with the archive's own ruling.** The widely told account: after the War of 1812, a peddler paid blacksmith Silas Hawes of Shaftsbury, Vermont, in worn steel saw blades; Hawes welded two at a right angle, making the first all-steel carpenter's square [FS2][FS3]. **The UVM finding aid calls the story "apocryphal,"** citing Kebabian [FS1]. The patent date is reported as 15 December 1819 by the UVM archival description and as 1817 by the Davistown Museum (citing the *Directory of American Toolmakers*); per UVM, "most of the patent records of the early nineteenth century — including Hawes' patent — were destroyed by fires" [FS1][FS2]. The archive's uncertainty is preserved rather than forced to one date. Some sources spell the name "Hawkes" [FS3]. **Related later tools** - **The [[Speed Square]]** — a separate triangular tool; Swanson dates it to 1925 (a maker claim) [FS4][FS28]. Fine Homebuilding: "when Albert Swanson showed up to work one day in 1925 with his invention, later patented as the Speed Square, his fellow carpenters all wanted to buy one" [FS4]. Related in trade use; its lipped-fence instructions do not transfer to the flat L. - **Precision workshop squares using the framing-square form (review fix 11)** — e.g. Woodpeckers' "OneTIME Tool — Precision Framing Square" (2018) and stainless squares, with a maker-stated tolerance of ±.0085° and no rafter tables. Woodpeckers' marketing says conventional framing squares "simply can't be trusted in tight tolerance shop work" [FS5]. This supports that maker's tolerance and intended uses, not a claim of descent or a broad revival. - **The Chappell Universal Framing Square** (US 7,958,645) — a 21st-century square for irregular, unequal-pitch roofs, marketed as "the first truly unique improvement to the framing square in over 110 years" [FS6] (marketing claim). **Contemporaries** - **[[Try Square]]** — bench-scale; tighter-tolerance local checks. - **Sliding T-bevel and combination square** — arbitrary angles, depth gauging. - **Steel-square books** — Hodgson (1880; condensed as *ABC of the Steel Square*, 1908, on Project Gutenberg) [FS7]; Siegele (1981) [FS8]; Riechers, *Full Length Roof Framer* [FS9]; Sigmon (1908, date flagged by its own bibliography) [FS10]. A small publishing genre devoted to teaching one tool's tables. --- ## history **Two eras.** The flat right-angle square is an old tool family; the industrial, table-stamped steel square as a trade product is a 19th-century American story, and that story's popular telling does not hold up against its company's own archive. **The Vermont manufacturing line (1810s–1920; UVM Special Collections and the Davistown Museum agree on names and sequence, differ on some dates).** Hawes partnered with Stephen Whipple, who built a waterwheel-driven trip-hammer mill in 1823 [FS1][FS2]. Small makers in the same valley followed — Dennis George, Jeremiah Essex, Heman Whipple, Lewis Beach, Hawks & Loomis, Rufus W. Bangs, Milo Pierce, Norman A. Douglass, May and Blackmer [FS2]. **Jeremiah Essex** gave his name to the **Essex Board Measure** table [FS1][FS11]. **Rufus W. Bangs** introduced "eccentric rolls" for tapering and finishing the blank [FS1]. **Millington & George** patented a "24 tool graduator" on 8 August 1854, cutting all graduations at once instead of hand-engraving up to 1,200 marks; the Davistown Museum holds its patent model [FS1][FS2]. These shops consolidated into the **Eagle Square Company** — incorporated 1859 per Davistown, informal origins c. 1846 and formal incorporation 1874 per UVM (unreconciled, flagged) [FS1][FS2]. A 1901–1906 shift to rolled 24"-wide sheet let a square be blanked from one sheet, ending the forged-and-welded process [FS1]. **Henry E. Harris** (at Eagle 1874–1926, superintendent its last 18 years) patented a take-down square in 1906 [FS1]. Eagle Square was sold to **Stanley Rule and Level Co.** in 1916; Stanley Rule and Level was absorbed into The Stanley Works in 1920 [FS1]. In 1937 Eagle Square employed about 100 people and shipped over 190,000 squares [FS1]. **The rafter table — a historically important specialist capability of many construction models (review fix 11), not the sole reason the form exists.** Plain L squares without tables remain useful for large local 90° layout and wide-stock marking. **Patent priority (review fix 7).** **Howard's US 247,353 (20 September 1881)** is an earlier located U.S. patent for a rafter-length table on a carpenter's square; its text describes "a carpenters square containing a table for determining the length of rafters for pitches and spans of roofs" [FS12]. **Nicholls's US 672,455 (23 April 1901)** describes a later and more elaborate system, including additional roof-layout relationships; Wikipedia credits it with "the traditional steel square's rafter table" [FS13][FS12]. Claims about which design established the later standard table layout are kept separate from patent-date priority. Later patents (Criss 1911, Sargent 1914, McLeod 1916, Esten 1927, Cramer 1940, Sigmon 1941) show continued re-engineering [FS12]. **Confidence on the wider patent sequence is lowered to MEDIUM** until each item is checked in the primary record (Run 306 reached these via a bibliography, not USPTO). **Stability.** Empire Level states the form "had remained much unchanged since the early 1900's, until 2015 when we introduced laser etched technology" [FS14] (maker claim). --- ## ✦ human side **Trades.** Roof framers and carpenters; stair builders, who clamp stair gauges to the square at rise/run marks to repeat a stringer pattern [FS15]. **Named hands.** - **Larry Haun** (1931–2011) — union framing carpenter and author (*The Very Efficient Carpenter*). Fine Homebuilding's material on his method describes laying out one common rafter with a framing square, cutting it, and using it as the pattern for the rest [FS16] (summary-level source). - **Dave Osborne** — self-described 50-year journeyman carpenter, foreman and contractor; worked rafter example and the field mnemonic "Mark this rafter PAT... it's for 'pattern'" [FS17]. - **Peter Toomey** — master carpenter since 1984 (All Seasons Decks & Gazebos), inventor of US 11,654,545 B1; his company's field guide to roof-framing mistakes is commercially motivated but specific [FS18]. - **Paul Sellers** — on local vs whole-assembly checking (see *matching*) [FS19]. - **Justin Fink** — Fine Homebuilding survey of rafter squares (2020/21) [FS4]. - **Suzanne Bacheller**, "Silas Hawes – Early Squaremaker," *Chronicle of the Early American Industries Association* 63, no. 4 (2010): 160 — citable, paywalled, unread [FS3]. **Stories.** Fine Homebuilding forum thread titles "The Revered Framing Square" and "Framing Square — Mystery Tables" [FS20]. This Old House's Tom Silva advises a beginner's first square be "a 12-inch speed square" [FS22]. Modern construction calculators and layout apps offer alternative workflows; correct table use remains viable when its assumptions and reference lines are understood (review fix 12 — the former "most carpenters never learn the tables" and "calculators are much more accurate" claims, from search snippets, are removed). --- ## ✦ proof of existence - **Bennington Museum, VT** — "an early Silas Hawkes framing square, dated to 1818" [FS3] (via bibliography; catalog page not reached). MEDIUM. - **Smithsonian NMAH** — carpenter's square, ID 1997.0097.1199, Accession 1997.0097, gift of Teodoro Vidal, Puerto Rico, 20th century [FS36]. HIGH on the accession. - **UVM Special Collections** — Eagle Square Manufacturing Company Records, 1847–1962 (mss-289), 74 linear feet [FS1]. HIGH. - **Davistown Museum** — objects 121906T1 ("S. HAWS PATENT WARRANTED STEEL"), 040103T9 ("HAWES patent 1825" — a date matching neither patent claim, flagged), 63001T3 ("J. Essex CAST STEEL WARRANTED No. 1"), and the 1854 Millington & George graduator patent model [FS2]. - **Patents** — US 22,585 (Ripley, 1859); US 247,353 (Howard, 1881); US 672,455 (Nicholls, 1901); US 1,007,539 (Criss, 1911); US 1,102,689 (Sargent, 1914); US 1,189,983 (McLeod, 1916); US 7,958,645 (Chappell); US 11,654,545 B1 (Toomey) [FS12][FS18]. Via bibliography; primary-record checks pending. MEDIUM. - **Trade literature** — Hodgson 1880/1908 on Project Gutenberg [FS7]; Sears catalogs 104 (1897) and 111 (1902) digitized but not opened (lead only) [FS37]. --- ## references - [FS1] University of Vermont Silver Special Collections, "Eagle Square Manufacturing Company Records, 1847-1962" finding aid (mss-289) — scfindingaids.uvm.edu/repositories/2/resources/1213; cites Kebabian, *American Woodworking Tools* (1978), p. 188. *archive* - [FS2] Davistown Museum, toolmaker biography — davistownmuseum.org/bioEagleSq.htm; citing DATM (1999). *museum* - [FS3] InspectAPedia, "Framing Square Manuals, Books & Downloads" — inspectapedia.com/roof/Framing-Square-Manuals-Downloads.php. *specialist bibliography* - [FS4] Fink, Justin, "The Indispensible Rafter Square," *Fine Homebuilding* 296 — finehomebuilding.com/project-guides/framing/the-indispensible-rafter-square. *magazine* - [FS5] Woodpeckers, "OneTIME Tool — Precision Framing Square"; stainless squares — woodpeck.com. *maker material — its own tolerance and uses only* - [FS6] Chappell Universal Framing Square copy (via [FS3]); Wikipedia "Steel square." *marketing/encyclopedia* - [FS7] Hodgson, *The Carpenters' Steel Square and Its Uses* (1880); *ABC of the Steel Square* (1908) — gutenberg.org/files/49273/49273-h/49273-h.htm. *book* - [FS8] Siegele, *The Steel Square* (1981). *book* - [FS9] Riechers, *Full Length Roof Framer* — archive.org/details/fulllengthrooffr0000afjr. *book* - [FS10] Sigmon, *A Framing Guide and Steel Square* (1908; date flagged). *book* - [FS11] Friedman, "Essex Board Measure Table on a Framing Square" — inspectapedia.com/roof/Essex-Board-Measure.php. *specialist* - [FS12] Patent bibliography via [FS3] (numbers and dates listed under *proof of existence*). *patents via bibliography — primary checks pending* - [FS13] Wikipedia, "Steel square." *encyclopedia* - [FS14] Empire Level, "Framing Squares" — empirelevel.com/framing-squares.php. *maker* - [FS15] Empire Level, 105 Brass Stair Gauges (same page). *maker* - [FS16] Fine Homebuilding, Larry Haun roof-framing material — finehomebuilding.com/project-guides/framing (summary-level). *magazine* - [FS17] Osborne, Dave, "The Framing Square, Rafter Square or Steel Square" — daveosborne.com/dave/articles/framing-square.php. *practitioner* - [FS18] Toomey / Rapid Rafter, "10 Roof Framing Mistakes" — rapidrafter.com/learn/10-roof-framing-mistakes. *practitioner/commercial* - [FS19] Sellers, Paul, "When not to use a Square" — paulsellers.com/2022/10/when-not-to-use-a-square/. *teaching* - [FS20] Fine Homebuilding forum thread titles — finehomebuilding.com/forum/the-revered-framing-square. *forum (titles only)* - [FS21] ContractorTalk threads (storage, tables) — search summary only. *forum, reduced confidence* - [FS22] This Old House, "Choosing and Using Squares: A Comprehensive Guide" — thisoldhouse.com/tools/choosing-and-using-squares. *trade press — also the source identifying the hook-the-lip saw technique as a Speed Square technique (the reviewer)* - [FS23] Johnson Level & Tool, "How to Use Framing Square" — johnsonlevel.com/News/FramingSquare; CS9 spec. *maker instructions* - [FS24] Toolstash, "Framing Square: Uses, Types, and How to Use It Right" — toolstash.com/terms/framing-square. *retailer teaching* - [FS25] Johnson CS9 retail listings. *retailer* - [FS26] Irwin Steel Carpenter Square (1794462); Aluminum Framing Square (1794448) — irwintools.com. *maker* - [FS27] Empire e1190 at Home Depot; Empire 1140/1140M. *retailer/maker* - [FS28] Swanson Tool Co., TA122/TA127 Rafter Square; black anodized square — swansontoolco.com. *maker (summary-level)* - [FS29] Toolstash care and mistakes sections (as [FS24]). *retailer teaching* - [FS30] Wikipedia, "Steel square" — flip test. *encyclopedia (its center-punch repair advice is not relied on — review fix 4)* - [FS31] Search summary on table misreading — unverified. *low* - [FS32] Empire Level, "Rafter Squares" (small triangle) — empirelevel.com/rafter-squares.php. *maker* - [FS33] Irwin, Hi-Contrast Aluminum Rafter Square (1794463). *maker* - [FS34] Stanley, "Stanley® Framing Square Instructions" — support.stanleytools.com/hc/en-us/articles/360012679138-Stanley-Framing-Square-Instructions. *maker instructions* - [FS35] Home Depot breadcrumb taxonomy for the Empire e1190. *retailer* - [FS36] Smithsonian NMAH, carpenter's square, 1997.0097.1199 — americanhistory.si.edu/collections/object/nmah_602569. *museum* - [FS37] Sears, Roebuck catalogs 104 (1897) and 111 (1902) — archive.org. *lead only* - [FS38] Smithsonian NMAH slide-rule collections — distinction between sliding logarithmic scales and fixed tables. *museum (the reviewer; URL to be supplied)* - [FS39] Swanson Tool, current roof-pitch and common-rafter instructions — ridge-correction wording depends on method and reference. *maker instructions (the reviewer; URL to be supplied)* - [FS40] Bosch and Makita circular-saw instruction manuals — clamping, work support, guide/clamp clearance, binding and kickback. *manufacturer manuals (the reviewer; model/URL to be supplied)* --- ## forge images needed 1. **Anatomy callout, face and back** — body/blade, tongue, heel; tables labelled "where present." 2. **The naming collision** — five panels for "rafter square." 3. **Local corner vs whole assembly** — a frame with one checked corner and two diagonal tapes. 4. **No lip** — side-by-side Speed Square (lipped fence) and flat framing square, captioned "this technique does not transfer." ## The reviewer's corrections (12) - `BLOCKER` — 1. Correct the circular-saw guide procedure — Exact claim: “Hook the tongue’s lip against a board’s edge and run a circular saw’s base plate along the body,” with movement characterized as a cut-quality and control issue rather than a documented injury mechanism. - `BLOCKER` — 2. Make rafter and ridge deductions method-specific — Exact claim: Find the pitch row, multiply its length-per-foot-of-run figure by the run, “then subtract half the ridge-board thickness.” - `BLOCKER` — 3. Condition beginner access by operation — Exact claim: The basic 90-degree and straightedge functions are “beginner-safe immediately,” while the matching material also includes wall frames, roof rafters, stairs, and circular-saw guidance. - `SHOULD-FIX` — 4. Remove generalized center-punch and hammer truing advice — Exact claim: An out-of-square framing square can potentially be corrected with a soft hammer or center punch. - `SHOULD-FIX` — 5. Correct the physical and mathematical identity — Exact claim: It is a “single flat piece … bent to 90°,” “literally a slide-rule,” and embodies “all of trigonometry.” - `SHOULD-FIX` — 6. Scope dimensions, tables, and materials to actual variants — Exact claim: The entry often treats the 16-by-24-inch size, full table set, and steel/aluminum behavior as defining properties. - `SHOULD-FIX` — 7. Reframe Howard and Nicholls patent priority — Exact claim: Howard’s 1881 patent and Nicholls’s 1901 patent represent a “contested first” for rafter tables. - `SHOULD-FIX` — 8. Bound historical lineage claims — Exact claim: The try square is a “direct conceptual ancestor,” and early iron squares establish an ancient, continuous line into the table-bearing framing square. - `SHOULD-FIX` — 9. Resolve the large-assembly matching contradiction — Exact claim: The square checks wall frames, deck framing, and door or window openings, while another section says it is not for testing a large finished assembly “at all.” - `SHOULD-FIX` — 10. Separate intrinsic tool risk from matched-operation risk — Exact claim: The dangerous-use class is thin because no specific framing-square injury was found. - `SHOULD-FIX` — 11. Temper specialist-purpose and revival claims — Exact claim: Rafter tables are the “actual reason for existing,” and precision workshop squares are descendants or evidence of revival. - `SHOULD-FIX` — 12. Remove prevalence and accuracy claims supported only by snippets or forums — Exact claim: Most carpenters never learn the tables, and calculators are “much more accurate.”