# Sashigane

Hewn Tool Library · https://hewn.build/tools/sashigane

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: "Sashigane." Hewn Tool Library, hewn.build/tools/sashigane. Reviewed 2026-07-30.

---

## identity

- **name:** sashigane — written 差し金, 差金, 指金 or 指矩; also **曲尺 (kanejaku)**, and called *kane-shaku* or *magarigane* [KB1][SG8]. Spellings are variants; none is presented as the single canonical form. English retailers often sell it as "Japanese Square" [SG26].
- **family / category (review fix 1):** Layout and Marking Tools → fixed-angle metal squares. A **Japanese metal carpenter's square** used for measuring, checking right angles and laying out lines [KB1][SW-C][SG8].
- **constructions (model-specific):**
  - **flexible, thick-corner** — thin arms that can flex while the thicker corner helps preserve squareness and register the corner against the work [SW-C][SG26];
  - **uniform-thickness** — the corner the same thickness as the arms (e.g. Shinwa 10510, 2.6 mm, used for joinery) [SW-C][SW-10510];
  - **heavy non-flexing section** — explicitly designed not to flex, for higher marking pressure and joinery, furniture, civil or steel work [SW-S];
  - *(thin-corner forms are documented by Shinwa but not currently sold as of its page update [SW-C].)*
- **scales (review fix 2):** many traditional or calculation-scale models include kaku-me and/or maru-me; others repeat ordinary scales on both faces, use metric/imperial faces (Lee Valley's export model), or carry other special graduations (mortise-depth, division) [SW-G][SG26]. **Verify the actual graduations on the specific square.**
- **one-line:** a Japanese metal L-square for measuring, right-angle checking and line layout, whose construction (flexible, uniform or heavy) and graduations (plain, metric/imperial, or calculation scales) vary by model.

---

## ✦ How NOT to use it

### dangerous — concrete controls (review fix 9, the holding finding)

The sashigane is lower-energy than a powered tool, but "no moving parts" and "no cutting edge" do not remove risk. Its **own metal edges or corners may be sharp or burred**, a **flexible arm can spring back**, and layout puts a **marking knife, awl, scriber or sumisashi** moving beside the stabilizing hand [the reviewer safety notes][SW-S].

- **Inspect before precision work:** burrs, cracks, corrosion, kinks, and loss of squareness.
- **Flex only a model intended to flex,** in the maker-described direction, and only enough to register it; **control the return** — do not release it under tension [SW-C][SG10].
- **Keep the holding hand behind the travel** of a marking knife, awl or scriber, and direct the stroke away from the body.
- **Use a section stiff enough for the marking pressure;** Shinwa describes heavy B-sections for pressure from precision marking tools [SW-S].
- **Never use a thin flexible sashigane as a guide for a saw, router or other powered cutter** unless the tool and guide makers explicitly authorize that setup and the guide can be securely retained.
- **Store and transport** so the arms do not kink and the corners and edges cannot snag or cut.
- **Recheck squareness** after a drop, overload, visible bend or uncontrolled springback.

*Do not infer safety from an unsuccessful incident search.* The build's search found no injury account; that is a research result, not a risk assessment.

### damaging
- **flexing the wrong way, or too far** — inaccurate lines; possible permanent set [SG10].
- **poorly reinforced copies** — a practitioner review says inferior copies lack the reinforced corner and standard measurement [SG18].
- **heavy marking pressure on a thin flexible model** — choose a heavy section instead [SW-S].
- **treading on it** — the traditional job-site reprimand records how the trade regards mishandling [SG8].

### beginner-trap
- **front vs. back scales** — Rex Walters: "This confuses many people. To the point that manufacturers now also make them available with identical scales on both sides" [SG5]; JREF thread [SG11].
- **assuming calculation or shaku/sun scales are present** — verify the SKU [SG20][SG26].
- **assuming 45° is built in** — it depends on scale, technique or a stopper [SW-ST].

### lineage-misuse
- **handling a rigid Western try square like a flexible sashigane,** or assuming every sashigane flexes — flex behavior is model-specific [SW-S][SG7].
- **expecting printed rafter tables** — see *matching* (review fix 11).
- **trusting the name for construction** — rigid squares are also sold as "sashigane" [SG23].

---

## correct use
*Short — the workbench holds operation.*

- **identify the form and the scales first** — flexible, uniform or heavy; plain, metric/imperial or calculation scales [SW-C][SW-G].
- **ordinary use:** measure length, check right angles, lay out straight lines against the edge with pencil, ink, scriber or knife suited to the section [SW-S][SG9].
- **flexing (flexible models only):** flex in the maker-described direction, only enough to register; Fukata: the square "is designed to maintain its accuracy in the width direction, even when it bends in the thickness direction... Bending it in the wrong direction can lead to inaccurate lines" [SG10][SW-C].
- **calculation scales:** use kaku-me / maru-me only on a model that has them and only for the problem they solve [SW-G].
- **45° and slope work (review fix 10):** technique-, scale- or accessory-dependent; Shinwa describes 45° lines with a fitted stopper [SW-ST].

---

## ✦ matching — keyed to form and graduations (the reviewer schema notes)

**First ask: which form and which graduations are present?**

- **flexible thick-corner** — ordinary layout; conforming an edge against some curved or irregular surfaces [SW-C][SG26].
- **uniform thickness** — general measuring and pencil/scriber layout where full-face registration helps [SW-C].
- **heavy non-flexing section** — joinery, furniture or marking that applies greater pressure [SW-S].
- **calculation-scale model** — adds square-from-round (kaku-me) and circumference (maru-me) work [SW-G].
- **plain imperial/metric or same-scale model** — ordinary measuring and square layout only, unless other scales are explicitly present [SG26].
- **accessory-equipped model** — stopper/fence adds parallel lines, some 45° work, thickness/diameter comparison, height measurement [SW-ST].
- **trades:** carpentry and building, joinery and furniture, civil work, steel work and DIY, depending on section [SW-S]; temple carpentry and kiku-jutsu as specialized contexts.
- **pairs with:** marking knife or kebiki, sumitsubo and sumisashi [SG9]; sliding bevel and precision rule [SG23].
- **vs. try square (task comparison):** IF the job is a 90° check at the required tolerance, THEN a sashigane can serve, depending on model stiffness, registration and tolerance (cited models specify ±0.1 mm/100 mm) [SW-10510][SG26]. Heavy or uniform sections suit pressure marking better than thin flexible ones.
- **vs. framing square (review fix 11):** a sashigane lacking Western rafter/brace tables does not duplicate those printed lookup functions. Traditional Japanese roof layout instead uses kiku-jutsu — specific scales, diagrams and training — a different workflow [SPR][SG27].
- **not-for (IF/THEN):** IF a cut needs a guide for a saw, router or other powered cutter, THEN do not use a thin flexible sashigane, unless the tool and guide makers explicitly authorize the setup and the guide can be securely retained. IF heavy marking pressure is needed, THEN choose a heavy section.
- **access (mandate rule — no beginner verdict; review fix 10):** a beginner can use it for length, right-angle checking and straight-line layout; calculation scales, 45°/slope work and kiku-jutsu need instruction. Handling requires the controls under *dangerous*.
- **revival:** active English-language practice and teaching (Rex Walters' series, Wabi Sabi School, Port Townsend) [SG2]–[SG5][SG29]; the calculation scales solve real geometry by hand.

---

## anatomy

| Part | Name | Note | Source |
|---|---|---|---|
| long arm | **nagate** (長手) / *chōshi* | traditionally ≈1 shaku 5 sun (≈454.5 mm); full-size current models ~500–525 mm | [SG8][SG22][SG26] |
| short arm | **tsuma-te** (妻手) / *tanshi* | conventional part name *(the "wife's hand" gloss is omitted — the reviewer mech. note)* | [SG8] |
| corner | **kanete** | **thick, thin or uniform** depending on model; a thickened corner is one construction used to help preserve squareness and ease registration while the arms flex — it does not make distortion impossible (review fix 7) | [SW-C][SG4] |
| corner insert (some brass models) | *kado-tetsu-iri* | triangular steel insert to resist distortion | [SG9] |
| section / edge profile | various (incl. *eguri*) | profiles differ for pencil, ink, scriber or knife and by trade; heavy B-sections resist marking pressure | [SW-S][SG22] |
| front scale | *omote-me* | ordinary graduations — shaku-sun, metric, or imperial depending on model | [SG8][SG26] |
| **kaku-me** (角目) | calculation scale (some models) | graduation **spacing is √2 × ordinary spacing**, so a diameter laid against it **reads approximately diameter ÷ √2 — the side of the largest inscribed square** | [SW-G] |
| **maru-me** (丸目) | calculation scale (some models) | graduations **compressed by π**, so a diameter **reads numerically as its circumference** | [SW-G] |
| other special scales | mortise-depth, division | model-specific | [SW-G] |
| mon-shaku / rohan-shaku | fortune scale | eight kanji divisions of non-structural significance, printed on many models | [SG8][SG10][SG11] |
| dimensions / tolerance | — | e.g. 15 mm width, 1.3 mm thickness (Dictum 717130); ±0.1 mm per 100 mm squareness on cited models — **product specifications, not family standards** | [SG22][SW-10510][SG26] |
| accessory | **stopper / fence** (some models) | adds parallel lines, some 45° work, thickness/diameter comparison, height measurement | [SW-ST] |

---

## variations (living) — dated examples (review fix 13)

*Observed during the 2026-07 build; prices and availability change.*

- **plain / same-scale-both-faces** — ordinary scales both sides [SG20][SW-G].
- **kakume / calculation-scale** — adds kaku-me and/or maru-me [SG20][SW-G].
- **metric/imperial export** — e.g. Lee Valley "Japanese Square": thin, pliable, reinforced corner, imperial and metric faces, hardened stainless, 0.1 mm/100 mm; no calculation scales stated [SG26].
- **flexible thick-corner** — e.g. Dictum/Shinwa 717130 (525 mm; listing describes ×3.14 and ×0.7 conversion scales) [SG22]; Nihonsan "thick corner" listings [SG24].
- **uniform-thickness, joinery** — Shinwa 10510 (2.6 mm, uniform corner, kaku-me/maru-me, ±0.1 mm/100 mm) [SW-10510].
- **heavy non-flexing B-section** — Shinwa section guide [SW-S].
- **compact** — ~10–15 cm reference squares [SG19][SG21].
- **current magnetic variant** — Shinwa 10435 [SG19] *(review fix 17: "no traditional precedent" removed)*.
- **rigid "sashigane"-branded square** — Dictum 717132 (title via search) [SG23].

Several current export listings use metric/imperial or metric-only graduations; other products retain calculation or traditional-unit scales (review fix 13).

---

## trades
- **daiku** (Japanese carpentry) and **miyadaiku** (temple/shrine carpentry, with kiku-jutsu) [SG9][SG10];
- **joinery and furniture, building, civil, steel work, DIY** — by section [SW-S];
- **Western woodworking** as an import, and in craft-school teaching [SG20][SG26][SG29].

---

## lineage

- **China — a cultural standard, not an invention record (review fix 3):** *Mencius* 4A.1 uses Gongshu Ban's skill to illustrate the necessity of compass and square — even he cannot make true forms without them [MEN1][MEN2]. Later tradition attributes many tools to Lu Ban, but this passage is not an invention record. The characters 曲尺 are shared with the Chinese *qūchǐ* [SG1]. The transmission path into Japan is **not established** here.
- **related Japanese squares:** **makigane** (smaller, thicker, more rigid) and **ogane** (large, site-built, for building outlines) [SG7].
- **current variants:** metric, traditional shaku/sun and metric/imperial graduation lines sold side by side; a current **magnetic** variant (Shinwa 10435, two 8 mm neodymium magnets in the short arm) [SG19][SG20][SG26].
- **contemporaries:**
  - [[Try Square]] — same 90° reference; Western try squares are typically rigid by construction.
  - [[Framing Square]] — Western framing squares carry printed rafter, brace and octagon tables; a sashigane without those tables does not reproduce that lookup function (see *matching*). Lee Valley sells a rigid, rafter-table "Carpenter's Stainless-Steel Square" separately from its flexible "Japanese Square" [SG26][SG27].
  - [[Speed Square]] (review fix 12) — adds a fence and pivot/angle graduations for common framing operations; it is a different form, not "a less precise sashigane." No precision ranking is made.
  - [[Marking Gauge]], marking knife, sumitsubo and sumisashi — the layout kit the square works with [SG9].

---

## history

- **design reading — a hypothesis (review fix 8):** flexible forms are well suited to conforming against curved stock, and thick-corner forms support that use [SW-C][SG6]; calculation scales solve square-from-round and circumference problems on the tool [SW-G]. Traditional Japanese carpentry worked extensively from round logs. *That this caused the flexible form to originate is a design-reading hypothesis, not proven history* — current forms also include rigid and heavy sections.
- **ink-marking edge profiles:** some sections are hollow-relieved or bevelled so marking tools ride the edge cleanly; Shinwa's section guide shows **multiple profiles for different marking tools and trades** — not every flexible sashigane has *eguri* [SW-S][SG4][SG22].
- **Hōryū-ji (review fix 6):** Hōryū-ji contains some of the world's oldest surviving wooden buildings, largely dating from the late seventh and early eighth centuries; UNESCO records destruction of the original buildings in 670 followed by rebuilding [UNESCO]. This does **not** date a sashigane.
- **kiku-jutsu (review fix 5):** kiku-jutsu (規矩術) has a documented historical literature and remains a living, taught, square-based roof-layout and marking discipline that can require long training [SPR][SG16]. *(The "Prince Shōtoku, 590 AD" origin and "Kamakura peak" claims came from unread search summaries and are removed pending direct review.)*
- **metrication (review fix 4):** per AIST's National Metrology Institute chronology, Japan joined the **Metre Convention in 1885**; the **1891** Weights and Measures Act kept shakkanhō as the base while adopting metric measures; **metric exclusivity was legislated in 1921** for implementation from 1924; and the principal full changeover was completed in **1959** [AIST]. The current Measurement Act governs non-statutory units today [JLT]. *Attributed practitioner account:* Rex Walters reports traditional squares marked "1/33 m" (≈30.3 mm, one sun) as a compliance workaround [SG3]; its origin and duration are unresolved here.
- **Shinwa:** formed 1971 by integrating three measuring-instrument makers; holds a 1977 patent for a stainless-rule graduation mass-production method [SW-H]. **A major current manufacturer** (review fix 13); not established as the single principal maker worldwide.
- **materials:** steel or brass historically, stainless from the early twentieth century; thickened brass corners on some models [SG8].
- **Himeji Castle claim — excluded:** a single-source blog claim resting on a date confusion; not carried [SG2].

---

## ✦ human side

- **Nishioka Tsunekazu (1908–1995)** — Tōryō of Hōryū-ji, led the restoration of Hōryū-ji and Yakushi-ji [SG12][SG13]. No source ties him to the sashigane by name; his kiku-jutsu practice makes it an inference, stated as such.
- **Kentarou Fukata** — Kyoto carpenter; practitioner blog and channel on kiku-jutsu and square mechanics [SG10] (credentials self-reported — MEDIUM).
- **teaching (review fix 15):** Suzuki-ya's product copy reports that Jay Van Arsdale (Laney College) recommends the plain version to beginners and Dale Brotherton (Port Townsend School of Woodworking) the kakume version to more advanced students [SG20] — **retailer-reported, not independently verified**. The Wabi Sabi School (Maine) lists it as course supply [SG29].
- **live confusion:** a JREF thread shows hobbyists unable to identify back scales until a moderator translated Shinwa's official Q&A explaining kaku-me, maru-me and the mon-shaku fortune scale [SG11].
- **trade reverence:** Japan House LA (with the Takenaka Carpentry Tools Museum) reports that stepping on a sashigane at a job site was traditionally met with sharp reprimand [SG8].

---

## ✦ proof of existence
- **museum:** Takenaka Carpentry Tools Museum, Kobe (opened 1984; 30,000+ objects) [SG14][SG15]; Japan House LA's "Masters of Carpentry" exhibition, produced with it, describes the tool's names, parts, scales and materials [SG8]. No individual accession record reached.
- **lexicography:** Kotobank / Japanese dictionaries for 指矩, 差金, 指金, 曲尺 [KB1].
- **scholarship:** kiku-jutsu literature (J-Stage abstracts; Springer 2025 "Kikujyutsu Assist") [SG16][SPR].
- **current manufacture and sale (review fix 14):** Shinwa product pages and catalogue features [SW-C][SW-S][SW-G][SW-10510]; current listings at Lee Valley, Dictum, Suzuki-ya, Osaka Tools, Nihonsan [SG19]–[SG26]. The tool is in active current manufacture and sale; no continuous-production claim is made.
- *(Moved out per review fix 18: the patent-search negative and one retailer's non-listing are research notes, not proof.)*

---

## references
*Weight noted per source.*

- **[SW-G]** Shinwa, "Various Scales of Carpenter's Squares" (曲尺の様々な目盛) — kaku-me, maru-me, mortise-depth, division scales. *(manufacturer — HIGH)*
- **[SW-C]** Shinwa, "Focus on the Corner" (「角」にこだわり) — thick, thin, uniform corners. *(manufacturer — HIGH)*
- **[SW-S]** Shinwa, section/profile guide (2023-08-21) — heavy non-flexing sections, trades. *(manufacturer — HIGH)*
- **[SW-10510]** Shinwa product 10510 — https://www.shinwasokutei.co.jp/products/10510/ *(manufacturer — HIGH for that model)*
- **[SW-ST]** Shinwa, carpenter-square stopper uses. *(manufacturer — HIGH)*
- **[SW-H]** Shinwa corporate history — https://www.shinwasokutei.co.jp/english/page/company/history.html *(manufacturer — HIGH for its own dates)*
- **[SG8]** Japan House LA / Takenaka Carpentry Tools Museum, "Masters of Carpentry" tools. *(museum partnership — HIGH)*
- **[SG26]** Lee Valley, "Japanese Square" (60N0315); **[SG27]** "Carpenter's Stainless-Steel Square" (60N4801). *(retailer — HIGH for listed specs)*
- **[SG22]** Dictum, Shinwa Flexible Sashigane 717130 — https://www.dictum.com/en/shinwa-square-sashigane-flexible/717130 *(retailer — model specs, not a family standard)*
- **[AIST]** National Metrology Institute of Japan, history — https://unit.aist.go.jp/nmij/info/history/ *(official — HIGH)*
- **[JLT]** Japanese Law Translation, Measurement Act — https://www.japaneselawtranslation.go.jp/en/laws/view/3027/en *(statute — HIGH, current law only)*
- **[MEN1]** Indiana University scholarly translation of *Mencius* (4A.1). **[MEN2]** Key Concepts in Chinese Thought and Culture, square-and-circle. *(primary in translation — HIGH)*
- **[KB1]** Kotobank, 指矩 — https://kotobank.jp/word/%E6%8C%87%E7%9F%A9-796307 *(dictionary — HIGH)*
- **[UNESCO]** Buddhist Monuments in the Hōryū-ji Area — https://whc.unesco.org/en/list/660/ *(HIGH)*
- **[SPR]** Springer Nature, "Kikujyutsu Assist" — https://link.springer.com/chapter/10.1007/978-3-031-94165-8_11 *(peer-reviewed — HIGH for current teaching/research)*
- **[SG16]** J-Stage kiku-jutsu abstracts. *(abstract level — MEDIUM)*
- **[SG1]** Wikipedia "Lu Ban" and secondary pages. *(LOW-MEDIUM; characters only)*
- **[SG2]–[SG5]** Rex Walters, "Sashigane" 1–4, rexs.tools. *(practitioner — MEDIUM; self-described as not authoritative on history)*
- **[SG6]** zo-d.com, sashigane vs. American steel square. *(blog — MEDIUM)*
- **[SG7]** Japan Woodcraft Association, marking tools. *(practitioner org — MEDIUM)*
- **[SG9]** Hida Tool, "Basics of Layout." *(retailer teaching — MEDIUM)*
- **[SG10]** Kentarou Fukata, carpentry-manual.com. *(practitioner — MEDIUM)*
- **[SG11]** JREF forum thread quoting Shinwa Q&A. *(forum — LOW-MEDIUM)*
- **[SG12]–[SG15]** Nishioka sources; Wikipedia "Japanese carpentry"; Takenaka museum site. *(encyclopedia / museum — MEDIUM / HIGH)*
- **[SG18]** Palo Coleman, Cool Tools review. *(practitioner review — LOW-MEDIUM)*
- **[SG19]–[SG24]** Osaka Tools, Suzuki-ya, Dictum, Nihonsan listings. *(retailer — dated specs and copy)*
- **[SG29]** Wabi Sabi School. *(school — MEDIUM)*

---

## research note (not evidence)
Build searches (2026-07) found no Japanese sashigane design/utility patent and no Highland Woodworking listing; a US design patent D510710 surfaced but is an unrelated Western square. Scope was not formally bounded; none of this is used as a finding.

---

## The reviewer's corrections (18)

- `SHOULD-FIX` — Exact claim: “A thin, deliberately flexible L-shaped steel square” and “fixed-angle reference squares,  …
- `SHOULD-FIX` — Exact claim: The tool is universally “marked with ordinary length units on its front face and two purpo …
- `SHOULD-FIX` — Exact claim: “Lu Ban … is credited by Mencius … with inventing the carpenter’s square.”
- `SHOULD-FIX` — Exact claim: “Japan’s traditional shakkanhou unit system was legally suppressed after the Meiji Restora …
- `SHOULD-FIX` — Exact claim: Kiku-jutsu “trac[es] to Prince Shōtoku’s era (590 AD)” and reached “a peak of development  …
- `MINOR` — Exact claim: Japanese carpentry from “the Asuka period (from 590 AD), the construction era of Hōryū-ji, …
- `SHOULD-FIX` — Exact claim: “The one part of the tool engineered to stay rigid, so the 90° reference itself never flex …
- `SHOULD-FIX` — Exact claim: A sashigane is “small, thin, and flexible” because traditional Japanese carpentry began fr …
- `BLOCKER` — Exact claim: “Safety profile: thin and benign,” followed by “no documented injury account … was found,” …
- `SHOULD-FIX` — Exact claim: A beginner can use it “as a simple 90°/45° reference square.”
- `SHOULD-FIX` — Exact claim: It “cannot replace” a framing square’s roof-calculation job because a sashigane “carries n …
- `SHOULD-FIX` — Exact claim: “The speed square trades precision for one-handed jobsite speed.”
- `SHOULD-FIX` — Exact claim: “The crossover hybrid is now the market-standard default for the export market,” “Every cu …
- `SHOULD-FIX` — Exact claim: Current listings prove “the tool has never left production long enough to require archaeol …
- `MINOR` — Exact claim: Named instructor recommendations on a retailer page are “a genuine, retailer-verified peda …
- `MINOR` — Exact claim: The sashigane “stayed small” while a framing square is “large.”
- `MINOR` — Exact claim: “Modern hybrid (magnetic) … with no traditional precedent.”
- `MINOR` — Exact claim: “No patent record found” and a “clean commercial negative” are used as proof-of-existence  …