Rafter squares measure and lay out straight, 45° angled, and 90° angled lines. Also known as speed squares, their flanged edge sits against a workpiece edge to check whether materials are square and to anchor the tool when marking lines. The flanged edge also provides a pivot point to measure and mark a range of angles. Their diagonal leg assists with marking rafter, trim, and stair angles. They are also used with plumb bobs when finding pitch on roof rafters and marking level lines along a plumb line.