What's inside
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A combination square and a try square both mark and check a 90-degree angle, but they suit different work. A try square is a fixed, simple reference for checking a board or marking a short line. A combination square adds a sliding rule, a movable head and extra functions. The right choice depends on how often you need to measure, mark and check—not on which tool has more features.
What each tool does
A try square has a blade fixed at 90 degrees to a stock, or handle. Set the stock against a board’s edge and the blade gives you a square reference across its face. Most woodworking try squares are around 150–300 mm long, though sizes vary. The fixed joint is straightforward: there is nothing to slide out of position during use.
A combination square has a rule that slides through a head and locks with a screw or knob. The head’s fence sits against an edge, letting you set a measurement and mark a line parallel to that edge. The head also provides a 90-degree face and, on many versions, a 45-degree face. Some rules include inch and metric graduations, a scriber, or a small level. Those extras are useful only if they work well and you use them.
Quick comparison
| Feature | Try square | Combination square |
|---|---|---|
| Checking 90 degrees | Fast and simple; fixed blade | Convenient, but head and rule must be set securely |
| Marking from an edge | Good for short, repeatable lines | Set a distance and repeat it along an edge |
| Adjustable depth | No | Yes; useful for shoulders, rebates and repeated marks |
| Other angles | Usually no | Often includes a 45-degree reference |
| Likely weak point | Blade or stock can be damaged or out of square | Rule can slip; a loose or poorly fitting head can give false readings |
| Best fit | Basic checking and occasional layout | Frequent measuring and marking at several distances |
Which one should you buy?
Choose a try square if your main job is checking that edges, ends and assemblies meet at 90 degrees, or marking short lines across stock. It is often the better value for a beginner who already owns a separate ruler. A basic, accurately made square is more useful than a feature-packed one that will not hold its setting.
Choose a combination square if you regularly mark a set distance from an edge, such as a 25 mm shoulder, a shelf-pin line, or a series of matching cuts. Sliding the head along the board makes repeated marks quicker than measuring each one with a tape. A combination square also replaces some jobs done with a separate small ruler and bevel reference.
For a first combination square, check that the rule slides without rocking, the lock holds under light pressure, and the graduations are readable. A long rule can reach farther across wide stock, but it is less convenient in a tool belt or crowded bench. A compact rule around 150 mm is handy for small parts; a 300 mm rule offers more reach for cabinet and site work. Pick a length that matches the pieces you actually lay out.
There is no need to buy an expensive combination square for occasional DIY if a cheaper one checks true and its head stays put. If accuracy matters across many projects, a better-finished head and clearer, durable graduations are worth paying for. Avoid choosing on the built-in level alone: a tiny vial is not a substitute for a reliable spirit level.
Browse woodworking try squares if you mainly need a fixed checking tool, or compare combination squares if you want adjustable layout. Check the stated rule length and graduation units before ordering; photographs do not always make scale obvious.
Check the tool before trusting it
Even a new square can be inaccurate. To test it, place the stock firmly against a straight, planed edge and draw a fine line along the blade. Flip the square over, register the stock against the same edge, and draw a second line from the same starting point. If the lines diverge, the tool is out of square. The gap at the far end is the error: a 1 mm gap over 100 mm means roughly 1 mm of error for every 100 mm of line.
Repeat the check before blaming the tool. A dent, rounded edge, pencil wobble or debris under the stock can imitate an accuracy problem. Use a sharp pencil or marking knife and a clean reference edge. For a combination square, repeat the test after locking the head, then check again after sliding it to another position. A head that shifts or produces different results is not dependable for layout.
Use it to reduce layout errors
Keep the stock flat against the board edge and hold it there without rocking. On a combination square, tighten the lock enough to prevent movement, but do not wrench it down; excessive force can damage the screw or distort the head. Before marking a batch of parts, set the rule once and test the distance on a scrap piece. A small reading error repeated across ten parts becomes a set of mismatched shoulders.
For a crosscut, mark from the face side and carry the line across the face and onto the adjacent edge when that helps guide a handsaw. For a shoulder cut, set the combination-square rule to the required depth, register the head against the edge, and mark consistently from the same reference face. Label that face if the part has been planed or its edges are not interchangeable.
Neither tool makes a rough board square. If the edge used as a reference is bowed, chipped or not at 90 degrees to the face, the square will faithfully transfer that error. Joint or plane a reliable edge first, or use a known straight reference. For larger panels and long crosscuts, a short square can establish a line but may not reveal twist or a poor saw path; check the cut with a longer straightedge or by comparing diagonals where appropriate.
Care and practical trade-offs
Keep the blade and rule free of glue, grit and rust. A small chip where the stock meets the blade can leave a visible gap and spoil a check. Store a try square where its blade cannot be bent, and retract or protect a combination-square rule so it does not get knocked in a tool bag. If either tool is dropped, retest it before using it on joinery.
For many carpenters, the useful setup is one combination square for measurements and repeat layout, plus a separate try square for quick checks at the bench. If you want only one, choose the combination square for versatility, but verify its accuracy and locking action. If you already have a dependable ruler and mostly check right angles, the simpler try square is a sensible, cheaper choice.