Adjustable, handheld, woodworking squaring jig that is stable, versatile, and easily maneuvered for the rapid and precise squaring of jointed cuts of varying size across various workpieces which can be used in various work environments, the jig being freely adapted to move across an axis of motion as to accommodate mortise and hinge plate notch cuts of varying sizes, the jig also having a plurality of clamping surfaces which allow it to be conveniently secured to a variety of workpieces and surfaces in different positions, as well as a plurality of slots which allow for the attachment of index clamps, screws or bolts to firmly attach the jig to itself and the mortise or notch cut to be squared.