- a thin flat piece of plastic, metal, etc, in the shape of a right-angled triangle, used in technical drawing
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Examples from the Web for set square
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.
For this purpose a tee-square and set-square are required, together with a pair of spring dividers and a sharply-pointed HB.
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