The framing square legs create both lines for you. Use the square to make one last final line that’s parallel with the first line you drew at the far end of the rafter.

Photo courtesy/Tim Carter A simple framing square, circular saw and a tape measure are just about all you need to make perfect angled roof rafter cuts. Those and a basic knowledge of trigonometry.

The Rafter Square, or Speed Square, does more than mark perpendicular lines. Here's how to make sense of all the numbers on your square and get the most out of this tool.