Rafter square adapts a sled to make miters
For accurate crosscuts on the tablesaw, I rely on a sled. I wanted that same precision for miters, but I didn't want to build another sled for 45° cuts. That's when I came up with this simple and inexpensive upgrade to my existing sled. All it takes is a plastic rafter square.
Begin by grinding or filing away one side of the square's lip so it lies flat. Align one corner of the square with the edge of the saw kerf in the sled, placing the square's longest side tightly against the sled's fence. Drill a 3⁄8 " hole through the square and into the sled, and install a threaded insert in that hole. Now you can quickly install the rafter square for 45° cuts, and remove it by using a star knob.
—Bill Wells, Olympia, Wash.