I use a saw protractor for many of my cut-off needs. It saves the step of drawing the cutting line on the material, and is highly accurate. I find it particularly useful for cutting bevels such as scarf-jointing 2x fascia boards.
Because most of my cuts are square, I have altered my protractor for long periods of use at 90°. To do this I set the protractor with a reliable framing square, tighten the wing-nut clamp, and drill a pilot hole through the calibrated arc into the arm. A self-tapping sheetmetal screw holds it at a perfect 90°, ready for all square cut-off needs. The screw is easily removable for angle cutting.
Ralph Dornick, Altoona, PA