A roof square for marking rafters comprising a right angle triangular body with a marking blade pivotally mounted adjacent the right angle. Either side of the square adjacent the right angle is held against the stock to be marked, and the blade used to mark either a plumb cut or a foot cut. The blade retracts to allow marks to be made at a measured depth. The tool can also be used as a conventional square to make 90 and 45 degree marks.