The Swanson Speed Square 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, and 5. protractor. The Speed Square is die-cast for durability and accuracy. Made of heavy-gauge aerospace Aluminum alloy, it is built to last. The Speed Square includes the Swanson Blue Book of rafter length and roof construction and features markings for using the Swanson one-number method of rafter layout. The Swanson Speed Square is our most popular product and remains the most trusted square of its kind. Look for the Diamond cutout for genuine Swanson products. Swanson Tool Company Speed Square W/Plain Markings, Blue Book | T0101