Although not as precise as Incra’s Protractor, Stanley’s Premium Adjustable Quick Square lets you mark angles in degrees and includes several handy scales for framing a roof. The square functions as a saw guide, a bevel for copying angles, and a protractor.
You set the angle on this 12″ square by moving the adjustable arm to match the correct reading on the scale and locking it down with a thumbscrew. Stanley coats the aluminum square in black to contrast the yellow graduations and make them standout in both sun and shade.
On their website, Stanley provides a comprehensive 60-plus-page manual on using the Quick Square, and includes definitions of common roofing terms and several reference tables. Pricing for the Quick Square starts around $13.