METRIC SPEED SQUARE 25 CM W/BLUE BOOK, EN/SP/FR PKG (10 IN. US) This is the 25 cm metric version of the Swanson Speed Square. The Swanson SpeedSquare was first developed by company founder Albert Swanson in 1925. This innovative tool combines 5 tools into 1: 1.Try Square,2.Miter Square,3.Saw Guide, 4.Line Scriber,& 5.Protractor. The SpeedSquare is die-cast for durability and accuracy. Made of heavy-gauge aerospace aluminum alloy, it is built to last. The Speed Square includes the SwansonMetric Blue Book of Rafter Length and Roof Construction and also features markings for using the Swanson One-Number Method of rafter layout. Look for the Diamond cutout for genuine Swanson products.