Try square

Also called: trysquare, set square, engineer's square

A try square is a fixed right-angle guide used to test whether an edge is square and to mark a straight line across wood.

Its parts

The blade is the thin steel rule, and the stock is the thicker body that you hold against the work. On an ordinary try square the blade is fixed at a right angle to the inside face of the stock. Unlike a mitre square, which has its blade set at 45 degrees, a try square is for checking and marking a right angle.

Test an edge

Put the inside face of the stock against the reference edge and bring the blade onto the surface being checked. A continuous, even meeting tells you the edge is square to the reference; a visible gap shows where adjustment or further planing is needed. The tool can also help test the accuracy of prepared work.

Mark a joint

Hold the stock firmly against the board and draw along the blade with a pencil or marking knife. The resulting line gives a straight right-angle reference for cutting shoulders, setting out stiles or checking the end of a board. Keep the stock seated throughout the mark so the line does not drift.

Keep it trustworthy

Protect the blade and the inside face of the stock from knocks, dirt and damage. Check the square against a known straight edge from time to time, because a damaged or shifted tool can transfer its error to every line you mark.