How do I build roof rafters with a framing square?

To build a roof rafter using a framing square, you have to determine the pitch and length of the rafter with a calculator. You then use the square to mark the plumb line from the short leg, or tongue, to the longer leg (called the blade). This line is 12 inches long and is called the plumb cut. Now, using the length you determined with the calculator, take the same steps with your first rafter, adding the notch two inches from the plumb cut. This is the notch that will rest on the frame. Then, finishing up the board, measure the overhang, and, using the levels in the square handle, make a mark that squares the top. Now all that’s left is cutting the rafter to length and making the notch.