Measure, transfer or mark
Every layout job is some mix of three actions (see the plate above). Measuring reads a number off a scale. Transferring carries a size or angle from one place to another without a number. Marking leaves the line you will cut to. Numbers have their place — a drawing gives them, and a board has to start somewhere — but every reading and every written figure is a chance for a slip. The published guide to measuring and marking makes the case in full: where one part must fit another, transfer from the part.
Tools that measure
- Steel rule. The reference for short measurements: rigid, with graduations right to the end and no hook to wear. Stood on edge, its graduations touch the work, which avoids reading at an angle.
- Tape measure. Long measurements and rough stock. Its sliding hook is designed to allow for its own thickness; a bent hook upsets that — see tape hooks.
- Calipers. Inside, outside and depth measurements of thicknesses, holes and tenons, where a rule cannot reach.
- Protractor and angle finder. Read an angle as a number, for setting a saw or a bevel. Starrett states its combination square’s protractor head as accurate to 15 minutes of a degree.
- Straightedge. Measures nothing, but checks: is a surface or edge straight? Veritas grinds its steel straightedges flat to within 0.0010 in over 12 and 24 in.
How accurate is a rule or tape?
There is no single answer, and a tape’s printed class is the most useful clue. In the United States, weights-and-measures law sets how far a measure used in trade may be out; in Europe, tapes are sold in accuracy classes and marked with them. Neither is a promise about a particular tape in your hand, but they show how much two ‘correct’ tapes can disagree — which is why the same tape should be used for a whole project.
| Measure | Stated tolerance | Source and scope |
|---|---|---|
| Metal tape, up to 6 ft | ±1/32 in | NIST Handbook 44: US tolerance for measures used in commerce |
| Metal tape, 7 to 30 ft | ±1/16 in | NIST Handbook 44 |
| Rigid rule, up to 6 in / 1 ft / 2 ft | ±1/64 / ±1/32 / ±1/16 in | NIST Handbook 44 maintenance tolerances; new measures are held to half |
| Tape, EC class I | ±1.1 mm over 10 m | BMI, a tape maker |
| Tape, EC class II | ±(0.3 + 0.2 L) mm, L in metres — ±2.3 mm over 10 m | Richter (formula) and BMI (10 m figure), tape makers |
| Tape, EC class III | ±4.6 mm over 10 m | BMI |
| Steel straightedge, 12 or 24 in / 36 in | Flat within 0.0010 / 0.0015 in | Veritas, for its own straightedges |
Tolerances allowed for measures used in trade, not the tested accuracy of any tape. Convert between fractions and millimetres with the fraction and metric chart.
Tools that transfer
- Dividers and compasses. Carry a distance from the work to the work, step off equal spaces, and scribe arcs and circles. A woodworking compass is the same tool with a pencil in one leg.
- Marking gauge. Carries a distance from a face or edge and repeats it on every part; see the marking gauge guide.
- Sliding bevel. Carries an angle from a drawing, a joint or an existing piece without reading it.
- Combination square, set. A locked blade repeats a distance or depth; see the square guide.
- Story stick. A strip marked full size with every position a set of parts needs, transferred without a number.
Tools that mark
- Marking knife. A fine, cut line to saw or pare to exactly.
- Pencil. Rough marks and anything that must not be scored into a show surface; choosing one is covered in how to choose a pencil for woodworking.
- Awl. Marks a point — a hole centre, the end of a line — with a small dent that a drill point or a knife can find.
- Scribe. Transfers an irregular outline, such as a wall or an uneven floor, onto a part so it can be cut to fit.
Which tool for which task
| Task | Tool | Why |
|---|---|---|
| Cut a part to a drawing dimension | Steel rule or tape, then a knife and square | The number comes from the drawing, so read it once, carefully |
| Fit a part to another part | Mark directly from the part | No reading, no arithmetic, no disagreement between rules |
| Repeat one distance on many parts | Marking gauge or set combination square | Set once, repeated exactly |
| Copy an angle | Sliding bevel | Carries the angle itself, not a reading of it |
| Set a saw or fence to an angle | Protractor or angle finder | Here a number is what the machine needs |
| Space holes or parts evenly | Dividers | Step off equal spaces without dividing numbers |
| Check a surface or edge | Straightedge | Light under it shows the high and low spots |
| Mark a hole centre | Awl | A dent the drill point can find |
| Fit to an uneven wall | Scribe or compass | Follows the outline directly |
The measuring pilot gives the method behind all of these: how to measure and mark accurately. The two tools most layout depends on have their own guides — squares and marking gauges.
Sources
Tape and rule tolerances are from the US weights-and-measures code and the EC accuracy classes as tape makers publish them; they describe what a measure used in trade may be out by, not the accuracy of any particular tape. Straightedge figures are the maker’s own. Which tool suits which task is established bench practice.
- 1.
NIST Handbook 44 (2026), Section 5.52: Linear Measures. National Institute of Standards and Technology, 2026.
Used for: US weights-and-measures tolerances for linear measures used in commerce: metal tapes ±1/32 in up to 6 ft and ±1/16 in from 7 to 30 ft; rigid measures ±1/64 in up to 6 in, ±1/32 in at 1 ft and ±1/16 in at 2 ft (maintenance tolerances, acceptance half those); graduations no wider than 0.75 mm.
- 2.
Accuracy table according to EC class II. Friedrich Richter Messwerkzeuge (Richter).
Used for: The EC class II tolerance for measuring tapes: ±(0.3 + 0.2 L) mm, L in metres.
- 3.
Measuring tapes: need to know. BMI.
Used for: EC accuracy classes for tapes: class I ±1.1 mm, class II ±2.3 mm and class III ±4.6 mm over 10 m, at 20 °C and a stated tension.
- 4.
Veritas Steel Straightedges. Veritas Tools Inc..
Used for: Edges ground flat to within 0.0010 in (12 and 24 in) and 0.0015 in (36 in), stress-relieved to stay true.
- 5.
Frequently Asked Questions on the Starrett Combination Square. L.S. Starrett Company.
Used for: A combination square’s protractor head accurate to 15 minutes of a degree.
About this guide
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