As a saw guide, stair layout tool or rafter tool, Johnson's 12" rafter square will help you get the job done accurately and easily. It features Johnson's unique Structo-Cast® molded frame that is both lightweight and durable, as well as permanent molded graduations for making quick and easy measurements. This rafter square comes with handy markers that measure 2x4 board dimensions of 1-1/2", 3" and 3-1/2". And you'll always find this square quickly in your toolbox thanks to its fluorescent, easy-to-see color.