As a saw guide, stair layout tool or rafter tool, Johnson's 7 inch 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. This rafter square comes with handy markers that measure 2x4 board dimensions of 1-1/2 inch, 3 inch and 3-1/2 inch. And you'll always find this square quickly in your toolbox.