Abstract: A square gauge apparatus configured for being selectively and removably mounted on a leg of a carpenter's square has a ledge having a ledge first surface and an opposite ledge second surface, the ledge first and second surfaces being parallel and offset, a first abutment extending from the ledge and having a first abutment front surface that is perpendicular to the ledge first surface, a second abutment extending from the ledge opposite the first abutment and having a second abutment front surface that is perpendicular to the ledge second surface and parallel to and coplanar with the first abutment front surface, and a slot formed adjacent to the ledge between the first and second abutments, the slot having a slot end surface that is parallel to and coplanar with the first and second abutment front surfaces.

Abstract: A multi-function pair of square gauges for a steel square, the more common of which are referred to as framing or rafter squares. The square gauges give the steel square 90 degree abutments which are in precise vertical alignment with the square blades vertical edge, which essentially turn a carpenter's square into a try square. They also give the square ledges which self-support the square when in normal use. They can also be positioned on the square as a length or depth gauge for marking framing stud layout or repetitive cut lines, and can also be positioned as an improved set of stair or rafter gauges.