This 12 in. Johnny Square is a versatile tool for builders and contractors. Its thick edge is useful as a saw guide - it can be used directly with the saw against the square for crosscuts or angled cuts using the etched protractor scale. It can be used indirectly as well, using the scribing notches to create a saw cut line for rip cuts. The Johnny Square also simplifies stair layout - its integrated distance and angle scales let you quickly and accurately mark your cut lines on your stringers. And, of course, this rafter square has scales for cutting hip, valley and jack rafters.