Examples from the Web for set square
For this purpose a tee-square and set-square are required, together with a pair of spring dividers and a sharply-pointed HB.
Then the margins at the top and the two sides must be marked out, and the upright lines drawn in by means of the set-square.
And it is important that you should get these straight-edges at a true right angle, testing them carefully with the set-square.Stained Glass Work|C. W. Whall