Carpenter's Speed Square
by greengiant83, published
A speed square or rafter angle square is a triangular-shaped tool which combines some of the most common functions of the combination square, try square, and framing square into one. It is used to make basic measurements and mark lines on dimensional lumber, and as a saw guide for making short 45 and 90 degree cuts.
See Wikipedia for more information: http://en.wikipedia.org/wiki/Speed_square