A wooden try square is a modest tool, but it asks for exact work. Its purpose is to tell you whether an edge, shoulder, or joint is truly at right angles. If the square is inaccurate, every mark made with it carries the same error into the work.
Making one by hand is therefore not only a pleasant exercise in joinery. It is also a lesson in reference edges, controlled fitting, and verification. The finished square need not be elaborate. A straight hardwood blade, a stable stock, and a sound joint are enough, provided the parts are brought together carefully and tested before the tool is trusted.
The form of a wooden try square
A traditional try square has two principal parts:
- the blade, a long, narrow piece used for marking and checking;
- the stock, the thicker block held against the edge of a board.
The stock should be broad enough to register firmly against a workpiece, while the blade should be long enough for ordinary bench work without becoming awkward. For a small general-purpose square, a blade about 200–250 mm long, 30–40 mm wide, and 8–12 mm thick is a useful starting point. A stock around 70–90 mm long, 50–65 mm high, and 20–30 mm thick gives a comfortable bearing surface. These dimensions are suggestions rather than rules.
Choose a straight-grained, close-grained hardwood for both parts. Beech, maple, pear, ash, and similar woods can serve well when dry and free from twisting. The stock especially should be stable. Avoid pieces with knots, short grain, visible tension, or a strong tendency to cup.
Photo by Dominik Scythe on Unsplash.
Prepare the parts
Begin with pieces slightly oversize. Do not try to achieve final dimensions before you have established trustworthy reference faces.
For the blade, plane one broad face flat. Check it with a straightedge and by placing it against a known flat surface. Then plane one long edge straight and square to that face. Mark these two surfaces clearly with a cabinetmaker’s mark or a small pencil triangle. They are your reference face and reference edge.
Prepare the stock in the same way. Flatten one broad face and make one adjoining edge square to it. The broad face will sit against the blade, while the lower or inside edge will bear against the workpiece. Keep your reference marks visible as you work.
It is worth leaving the blade and stock for a little time after rough preparation, particularly if the wood has recently been brought into a warmer or drier room. A small movement at this stage is easier to correct than movement after assembly.
Establish the shoulder
The blade must meet the stock along a clean, square shoulder. The shoulder supports the blade and prevents it from shifting while the glue sets. It also determines the visible inside corner of the square.
Place the prepared stock face down and mark the blade position across it. A blade set close to one end gives a compact square; leaving more stock below the blade provides a deeper bearing surface. Use the blade itself as a reference when laying out the width of the opening, rather than relying only on a ruler.
Transfer the layout around the stock with a marking gauge or knife. Mark the waste clearly. Saw the shoulder with a fine backsaw, stopping just on the waste side of the line. Remove the waste with a chisel, working from both faces toward the middle if necessary. Pare the shoulder gradually until the blade sits against it without rocking.
Do not force the blade into a tight, distorted socket. The fit should be firm and close, but the parts must meet naturally on their prepared faces. A joint that closes only under heavy pressure may spring out of alignment when released.
Fit and align the square
Before applying glue, assemble the dry parts. Hold the stock against a straight board and bring the blade into position. Look for gaps at the shoulder and check that the blade stands at a true right angle to the stock’s bearing edge.
At this stage, use a marking knife to identify high spots. Remove only the marked areas with a sharp chisel or plane. Keep returning to the dry fit. It is better to make several small corrections than one broad cut that leaves the joint loose.
If the blade passes through or partly into the stock, make sure its faces remain flush or intentionally offset according to your design. A slight proud edge can be planed level after assembly, but a hollow or twisted face is much harder to repair.
Photo by Austin Ramsey on Unsplash.
A simple first check
Place the stock against a straight reference edge, such as a carefully prepared board. Use a marking knife or sharp pencil to draw a line along the blade. Turn the square over and place the same stock edge against the same reference edge, with the blade now on the opposite side of the line.
If the two lines coincide, the square is close to true. If they form a narrow V, the error is revealed more clearly than it would be by simply looking at the corner. The farther apart the lines are at the end of the blade, the greater the error. This is a comparison test, not a substitute for a known straight reference edge, so choose the test board carefully.
Correct the joint before gluing if the error is significant. Pare the shoulder or adjust the bearing edge in small amounts, then repeat the test. Mark the direction of any error so that you do not remove material from the wrong side.
Glue and pin the joint
Once the dry fit and test are satisfactory, lightly scuff or clean only those surfaces that will receive glue. Apply a thin, even coat of wood glue to the joint. Excess glue can prevent the parts from seating fully, so avoid flooding the shoulder.
Bring the pieces together against a flat surface or a simple temporary guide. Check the blade immediately from both sides before the glue begins to set. A clamp can hold the assembly, but use moderate pressure. Heavy clamping may squeeze out too much glue or shift the blade.
Pins add useful mechanical security and suit the character of a traditional wooden square. Brass pins are durable and visible; wooden pins can be made from contrasting or matching stock. Drill through the stock and into the blade only after the joint is aligned. Use a drill bit suited to the pin and support the work so the bit does not wander.
Two small pins spaced along the joint are generally sufficient for a small square. If using wooden pins, leave them slightly proud and plane or pare them flush after the glue has cured. With brass pins, countersink only if you want the heads below the surface; do not enlarge the hole so much that the pin ceases to hold.
Let the glue cure fully before final shaping. The square should not be tested under pressure while the joint is still green.
Finish the blade and stock
After curing, plane the blade and stock flush where needed. Soften only the exposed corners with a very small chamfer. Keep the working edges crisp. A large roundover can make it difficult to place the square accurately against a line.
Plane the blade’s working edge straight and smooth. Check that the stock’s bearing edge is flat from end to end. If the square rocks on a board, find out whether the stock is hollow, twisted, or has a small raised area around a pin. Correct the cause rather than sanding indiscriminately.
For a wooden tool used at the bench, a light coat of oil or a thin hard-wearing finish is enough. Keep finish away from the actual bearing edges until their fit has been confirmed. Several thin coats are preferable to a thick coat that rounds the corners or changes the fit of the joint.
Mark the square with its date or a small maker’s mark if you wish. More importantly, mark the tested reference face. A wooden square can be used from either side, but its accuracy is easiest to understand when the reference edge is known.
Photo by Brett Garwood on Unsplash.
Test it before trusting it
Perform the line-flip test again after finishing. Use the same reference edge and place the stock in the same position for both marks. The lines should coincide or remain close enough for the work the square is intended to do. If they separate, identify whether the error is in the blade, stock, or test edge.
A second useful check is to test both the inside and outside corners against a straight board. The result should agree. You can also place the square against a known square corner, but remember that this only proves the two objects agree; it does not independently establish which one is correct.
For joinery, use the square with a marking knife rather than a soft pencil whenever the work allows. Set the stock firmly against the prepared edge and keep the knife upright. The square provides the direction, but a steady hand and a clean reference edge complete the mark.
Mistakes worth avoiding
- Using an unprepared edge as a reference. A square cannot correct a board edge that is already crooked.
- Choosing pretty but unstable wood. Figure, knots, and short grain can make a handsome tool that moves in service.
- Cutting the shoulder in one pass. Saw just inside the line and pare to the fit.
- Gluing before testing. A dry joint gives you freedom to correct the alignment.
- Over-clamping. Pressure can shift the blade or starve the joint of glue.
- Rounding the working edges. Keep the bearing and marking edges clear and deliberate.
- Skipping the final test. Assembly and finishing can both introduce small changes.
A handmade try square is not made dependable by ornament. It earns that trust through sound wood, a carefully fitted shoulder, restrained fastening, and repeated checking. Once true, it becomes a quiet reference on the bench: a small wooden instrument that helps every later piece of work begin in the right place.