As a saw guide, stair layout tool or rafter tool, Johnson's 12 in 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 in that are useful when transferring outside increments from the pivot point and handy markers that measure 2x4 board dimensions of 1-1/2 in, 3 in and 3-1/2 in.