As a saw guide, stair layout tool or rafter tool, Johnson's Johnny Square® 12" rafter square will help you get the job done accurately and easily. Its solid aluminum body construction with CNC machined edges provide greater accuracy and durability, while the low-glare, protective powder-coated finish makes the permanent graduations and numbers easy to read. This square also features scribe notches starting at 1-3/4" that are useful when transferring outside increments from the pivot point, and handy markers that measure 2x4 board dimensions of 1-1/2", 3" and 3-1/2".