Multi-function square gauges and methods of use

A square gauge apparatus for being selectively and removably mounted on a leg of a carpenter's square, the apparatus comprising:

• a ledge having a ledge first surface and an opposite ledge second surface, the ledge first and second surfaces being parallel and offset so as to define a ledge thickness;
• 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, whereby:
• the apparatus is configured such that placement of the leg of the carpenter's square within the slot with a leg edge against the slot end surface positions the leg edge parallel to and coplanar with the first and second abutment front surfaces and placement of the ledge on a workpiece with either the first or second ledge surface against a workpiece surface and either the respective first or second abutment front surface against an adjacent workpiece edge aligns the square leg edge with the workpiece edge at a desired location, rendering the carpenter's square accurate and versatile in multiple uses.