rafter angle square
A rafter angle square is a type of square, also called a speed square or magic square, that is commonly used in carpentry. A rafter angle square is typically made of cast aluminum. It combines some of the features of a protractor, a try square, and carpenter's square.
A rafter angle square is marked with degree gradations for fast, easy layout. It is small and therefore easy to carry and store. By positioning the square on a piece of lumber, it can be used as a guide when cutting with a portable circular saw.