BIG 12 SPEED SQUARE W/LAYOUT BAR, BLUE BOOK The Big 12 Speed Squareis a 12-inch 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. The Big 12 SpeedSquare is die-cast for durability and accuracy. Made of heavy-gauge aerospace aluminum alloy, it is built to last. 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. This model includes the SwansonBlue Book for Roof and Stairway Layout as well as theLayout Barfor use in determining out-of-square corners when building stairways. Look for the Diamond cutout for genuine Swanson products.