Empire 396 12 Polycast Rafter Marking Square A speed square is also known as the rafter angle square, rafter square, and triangle square. This is a multi-purpose triangular carpenter tool that is used for marking. Carpenters use it to make the basic measurement and mark lines on the dimensional lumber, and they see it as a guide for 45 to 90 degrees cut. The rafter square was made for scribing lines quickly. It has a lipped straight edge that provides 90 and 45 angles. Holding the lip of the rafter square against a board, you can mark out perfect perpendicular and 45 lines. You can do this as quickly as it takes to slide the rafter square around. Durable POLYCAST material Provides 90 and 45 angles Molded conversion tables Easy to see graduations repeated on both sides Made in the USA