A type of square that consists of a fixed, 90-degree angle. It is used mainly in woodworking, to lay out cutting lines at 90-degree angles, to check (or try) the squareness of adjoining surfaces, to check a joint to make sure it is square, and to check if a planed piece of lumber is warped or cupped... Found on http://www.daviddarling.info/encyclopedia/T/AE_try_square.html