The Big 12 Speed Squareis a 12" version of the Swanson Speed Square with added features for building stairs.
This innovative tool combines 7 tools into 1:
1.Try Square,
2.Miter Square,
3.Saw Guide,
4.Line Scriber,
5.Protractor,
6. Out-of-Square Corner Angle Finder,
7. Stair Layout Square.

die-cast for durability and accuracy. Made of heavy-gauge aerospace aluminum alloy.
Black-filled gradations stand out against a matte finish for easy reading and are simple to use with the Swanson One-Number Method of rafter layout.
Includes the SwansonBlue Book for Roof and Stairway Layout as well as theLayout Barfor use in determining out-of-square corners when building stairways.