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A try square is one of the quickest ways to check whether a small joint is actually square. It is useful for marking shoulders, checking the ends of tenons, setting out dovetails, and testing a freshly planed edge. For small joinery components, a compact square is usually easier to control than a full-size carpenter’s square, but the cheapest examples can introduce enough error to spoil a close-fitting joint.
What Makes a Good Try Square
A try square has a blade fixed at 90 degrees to a stock. The blade should be straight, the stock should sit flat against the work, and the joint between the two should remain rigid. Those requirements sound basic, but stamped blades, loose rivets, rough stocks, and poorly machined edges are common failure points.
For checking small components, look for a blade between 75 and 150 mm (3 and 6 inches) long. A 75 or 100 mm square is convenient for drawer parts, small boxes, and cabinet rails. A 150 mm square gives you a longer reference edge for checking a board end, but it takes more room on a crowded bench.
The stock should have a flat, reasonably wide face. A stock around 20 to 30 mm wide is comfortable to hold against an edge without rocking. A narrow stock can work, but it is less forgiving if the workpiece has a small chamfer or a rough patch.
The Best Types for Small Joinery
| Type | Best use | Advantages | Limitations |
|---|---|---|---|
| Machined engineer’s square | Checking tenons, shoulders, and small parts | Usually very accurate; compact; easy to use on a flat surface | Often lacks a broad stock for marking against a board edge |
| Traditional woodworker’s try square | Marking and checking cabinet parts | Comfortable stock; good visual reference; useful for layout | Quality varies widely; timber can move or wear |
| Combination square | General workshop work and repeated marking | Adjustable; includes a ruler; can mark 45 degrees | Bulkier; locking mechanism can develop play; more expensive |
| Mini or pocket square | Boxes, small drawers, and on-site repairs | Fits into a tool belt or apron; quick for short edges | Short blade makes small errors harder to see over longer distances |
For pure accuracy checking, a small 3-inch engineer’s square is often the safest inexpensive choice. It has a hardened or ground blade and a stock designed to hold the blade at a consistent angle. It is not as versatile as a combination square, but that simplicity is an advantage.
When a Wooden Try Square Makes Sense
A well-made wooden try square remains excellent for joinery. Its thick stock gives a clear reference against the edge of a board, and the blade is often easier to read when marking with a pencil or knife. It is particularly pleasant for dovetails and small mortise-and-tenon work, where you repeatedly register the square against the same face.
The risk is movement. A timber stock can swell in damp conditions or shrink in a heated workshop. If the blade is held by a loose pin or the stock has been dropped, the square may no longer be true. A quality 4-inch woodworking try square is worthwhile if you prefer this style, but a cheap decorative square is not a reliable measuring tool.
Check the blade for a clean, straight edge and inspect the stock for gaps around the blade. Avoid examples where the blade is visibly twisted or the stock rocks when placed on a known-flat surface.
How to Test a Try Square Before Trusting It
You can test a square without precision equipment. Place the stock against a straight, planed edge and draw a line along the blade. Flip the square over so the same stock face registers against the same edge, then draw a second line from the same starting point. If the lines diverge, the square is out of square. Over a 100 mm line, a gap of 0.5 mm is already noticeable in fine joinery.
For a more demanding test, use a flat reference surface and a feeler gauge. Set the square against a known-straight edge and check for light under the blade. Do not assume that a laser-etched scale proves accuracy; graduations can be correct while the blade is not at 90 degrees.
Also check for burrs. A burr on the stock or blade can hold the square away from the work by a fraction of a millimetre. That is enough to create a visible gap at the end of a tenon or leave a shoulder that needs excessive fitting.
Try Square or Combination Square?
Choose a try square when you mostly check fixed 90-degree joints and want the least possible play. Choose a combination square when you also need to set depths, mark parallel lines, or check 45-degree cuts. A good combination square is more versatile, but its sliding head has more parts that can loosen or collect dust.
For a small workshop, a reliable 100 mm try square plus a larger combination square is a practical pairing. If you are buying only one tool, a 150 mm combination square covers more tasks, provided the head locks firmly and the blade does not shift when pressure is applied.
Using a Square Without Fooling Yourself
Always check from the same reference face used during layout. A board can have one square-looking edge and another edge that is slightly out, so switching faces can produce conflicting results. On a tenon, check both cheeks and the shoulder. A tenon can be square across its width while its shoulder is angled along its length.
Keep the square clean and avoid dragging it through glue squeeze-out. Dried glue on the stock can create a false gap and may scratch a finely planed surface. Store a steel square dry, wipe it with a lightly oiled cloth when necessary, and protect wooden squares from extreme changes in humidity.
For most small joinery, spend money on accuracy rather than extra features. A basic, tested engineer’s square is fine for occasional box making, while a better-made wooden or combination square earns its cost when you mark and check parts every day. A compact 6-inch precision combination square is the more useful upgrade if your work includes both checking joints and setting out dimensions.