US Patent 7398601 Carpenter's pitch square

A carpenter's square includes a triangular base having first and second sides joined to form a right angle. A first elongated slot is disposed within the base parallel to a third side thereof; and a pin is selectively positionable along the length of the slot. The pin provides a mechanism for fixing the base in a specific orientation relative to an edge of an object when the pin is in a locked position within the slot.