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Marking a short rebate (also called a rabbet) is simple, but small errors show up quickly when the rebate is only 6–12 mm wide. A steel rule is accurate enough for this job if you use it against a reliable reference edge and control the marking point carefully. The aim is not just to read the measurement; it is to transfer it without allowing the rule, pencil, or knife to wander.
What you need
Use a rigid steel rule with clear graduations, preferably one marked in millimetres. A 150 mm rule is convenient for short rebates, while a 300 mm rule gives you more reach when marking across a wide board. A narrow rule is easier to hold against an edge, but a wider rule can be easier to read.
For the actual line, a sharp marking knife is the best choice when the rebate will be cut with a chisel or hand plane. A knife creates a crisp shoulder and gives the chisel a small track to follow. A sharp pencil is acceptable for rough work, softwood, or a cut that will be hidden, but a typical pencil line can be 0.5 mm or more wide. That is a large error on a 6 mm rebate.
You will also need a square if the rebate ends at an edge or must run square across the work. For repeated work, a woodworking marking gauge is usually faster and more consistent than measuring each board with a rule.
Choose the reference edge first
Decide which face and edge will locate the rebate. Marking from the wrong edge is one of the most common causes of a joint that is too loose or misaligned. If the rebate will receive another board, use the edge that will actually meet that board as the reference.
Inspect the edge before measuring. Remove obvious bumps with a block plane or sanding block, and make sure the edge is straight enough for the rule to sit against it. A small hollow can cause the rule to bridge the gap, moving the mark by a fraction of a millimetre. That may not matter on a rough shelf, but it matters on a tight housing or frame joint.
Put a small pencil tick on the reference face and edge if there is any chance you could turn the workpiece around. This is especially useful when marking several parts at once.
Mark the rebate width with the rule
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Place the workpiece on a stable bench with the reference edge facing you. If it rocks, fix that problem before marking.
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Hold the steel rule flat against the reference edge. Keep the rule square to the face rather than angled across it. The rule should make firm contact along its length without being forced.
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Find the required width. For example, if the rebate is 10 mm wide, align the zero mark with the reference edge and locate the 10 mm graduation on the face of the board.
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Make a small mark at the graduation. With a knife, keep the blade nearly vertical and make a light scoring cut. Do not press hard enough to let the blade follow the wood grain away from the intended point.
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Repeat the measurement at the other end of the rebate and at one or two points between them. If all the marks line up, place a straightedge against them and score the complete line.
Do not use the end of a rule as an automatic zero. Many rules have a rounded or worn end, and the first graduation may not be exactly at the physical end. If the rule is damaged, start from a clear graduation such as 10 mm and add the offset to your reading. For a 10 mm rebate, for example, align the 10 mm graduation with the reference edge and mark at 20 mm. This avoids errors from a bent or inaccurate rule end.
Knife, pencil, or marking gauge?
| Method | Best use | Main limitation |
|---|---|---|
| Marking knife and steel rule | Clean shoulders and visible joinery | Slower; the knife can follow grain if pressed too hard |
| Sharp pencil and steel rule | Rough work, softwood, and hidden rebates | Line thickness makes exact positioning less certain |
| Marking gauge | Repeated or long parallel marks | Needs careful setup and a reasonably flat reference face |
| Combination square with rule | Short marks that must be square and repeatable | Bulkier in tight spaces; cheap versions may have play |
For one or two rebates, a decent steel rule is usually the cheaper and perfectly adequate option. If you are making ten identical parts, the time saved by a gauge is worth more than the small cost difference. A 150 mm metric steel rule is a sensible general-purpose purchase; avoid very thin rules that flex when you press a knife against them.
Avoid common marking errors
Keep your eye directly above the graduation when reading it. Looking from an angle creates parallax, particularly with rules whose markings are recessed or printed on a raised surface. On a 10 mm measurement, a small viewing error is enough to spoil a tight fit.
Mark on the waste side of the line. The cut should remove the line, not leave half of it on the finished shoulder. If the rebate width is critical, make the knife line at the finished boundary and begin removing material on the waste side. A second, lighter line can identify the waste area, but do not create a confusing cluster of heavy marks.
Check the rebate depth separately. Width and depth are often confused because both may be marked from an edge. Use a combination square to transfer the depth from the appropriate face, or set a marking gauge from a known shoulder. If the rebate is 10 mm wide and 6 mm deep, write those dimensions on the workpiece before cutting.
Finally, test the setup on an offcut of the same material. Cut a short section and check the fit with the mating piece. This catches reversed reference edges, incorrect rule readings, and tear-out before the mistake reaches the finished board. When the fit is right, use the same reference face and edge for every matching part.