How to Use a Try Square to Check a Timber Cut End

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What a Try Square Does

A try square checks whether a timber cut end is at 90 degrees to the face or edge of the board. It has a stock, which bears against the timber, and a blade, which provides the reference line. A good square lets you check an end quickly without setting up a combination square or protractor.

This matters because a cut that is only slightly out can create a visible gap in a frame, throw a joint out of alignment, or make two boards meet at an angle. A 1-degree error over a 100mm-wide board produces roughly a 1.7mm gap at one side. That is enough to notice in trim work and joinery.

For general carpentry, a 150mm or 200mm try square is the most useful size. A 300mm square gives you a longer reference but is more awkward on small stock. Look for a rigid blade, a stock that sits flat, and a clearly readable inside corner. A cheap square is fine for rough framing if it is accurate; accuracy matters more than price.

If you need to buy one, compare 150mm try squares with larger versions before choosing. Avoid squares with a loose blade, a bent stock, or a corner that is visibly rounded where the blade meets the stock.

Prepare the Timber and Square

Make the cut end reasonably clean before checking it. Remove loose splinters with a sharp chisel or trim them with a handsaw. You are checking the actual cut surface, not a splinter that happens to stick out farther than the rest.

Brush away sawdust from both the timber and the square. A small chip trapped between the stock and the timber can shift the square enough to give a false result. Check that the timber face is reasonably flat as well. If the board is badly cupped, the stock may rock even when the cut is accurate.

Use a sharp pencil or marking knife if you need to mark the correction. Pencil is suitable for construction timber. A marking knife gives a finer line on furniture parts, but it can follow end grain and is less forgiving if your hand slips.

How to Check the Cut End

1. Place the timber on a stable surface with the cut end facing you. Hold the piece so it cannot roll or move as you check it.

2. Put the stock of the try square firmly against the timber’s face or straight edge. Keep the stock fully in contact; do not balance it on a corner or raised grain.

3. Slide the square until the blade touches the cut end. Do not force the blade into the timber. The square should contact the end lightly and evenly.

4. Look for daylight between the blade and the cut. Check at both the near and far edges, and preferably at the middle as well.

5. Turn the square over and repeat the check from the opposite side. This helps expose errors caused by a rounded edge, local tear-out, or a damaged square.

If the blade touches at one edge but leaves a gap at the other, the cut is out of square. Mark the high side or the waste side clearly before making another cut. On a wide board, check across several points because the saw may have wandered or the end may be slightly hollow.

Inside and Outside Checks

The inside corner of the square is normally the most useful reference. It lets you check the junction between the board face and the cut end without the blade being obstructed by the timber.

For a second check, place the blade against the end and use the outer edge of the stock against the timber. This is useful on narrow pieces or when the inside corner cannot reach a clean reference surface. Do not rely on one check alone if the timber has rough, damaged edges.

A square can be accurate on one side and misleading on another if its stock is worn or the blade is not seated correctly. If the result seems doubtful, test the square itself. Put it against a straight board, mark a line along the blade, then flip the square over on the same reference edge and mark again. If the lines do not coincide, the square is not reliable.

Correcting an Out-of-Square End

For a small error, clamp the timber and remove the high spot with a sharp bevel-edge wood chisel. Take light paring cuts with the bevel toward the waste where practical. Check often; it is easy to remove another shaving, but impossible to put one back.

A hand plane is better when the end needs a broader, controlled correction. A sharp block plane can trim the end of small sections, while a shooting board gives much better control for accurate joinery. Plane from the edge toward the middle on fragile or splinter-prone timber, then change direction if necessary.

For a larger error, remark the cut line and resaw the end with a handsaw. A fine-tooth panel saw gives a cleaner finish than a coarse framing saw. Leave the line visible and cut on the waste side, then finish with a plane or chisel.

Choosing the Right Square

A basic steel try square is enough for checking cut ends on construction timber and general workshop work. A heavier forged or machined square usually has a more durable stock and better resistance to knocks, but it costs more and may be unnecessary for occasional use.

For site work, a compact square that fits a tool belt is convenient, but very small squares can hide errors across a wide board. For furniture and cabinet work, a precise square with a fine blade is worth considering. You may also want small engineer’s squares for checking narrow parts and shoulder lines, though their stock is not always as convenient against rough timber.

Keep the square clean and do not use its blade as a scraper or screwdriver. Store it where the blade cannot be bent. Before important work, spend a few seconds checking it against a known straight edge. That simple habit prevents a faulty square from transferring the same error to every cut in a project.