A jig for cutting box joints on a table saw, including guide bar clamps adapted to be joined to guide bars of a table saw; a spacer joined to the guide bar clamps; a spacer strip joined to the spacer, the spacer strip defining spacer apertures; a board clamp joined to an engagement pin, the engagement pin engaging one of the spacer apertures of the spacer strip; and mechanism for offsetting pairs of boards such that grooves and projections on a pair of boards is cuttable offset from a corresponding pair and method of use including joining a jig to a table saw; clamping at least two pairs of boards to the jig; positioning the clamped boards relative to the table saw; cutting a groove through all boards; repositioning the clamped boards relative to the table saw; cutting another groove spaced apart from the first groove; repeating the steps of repositioning and cutting another groove until grooves have been cut from one edge to an opposing edge with projections disposed between the grooves; and interlacing the projections and grooves of the pairs of boards to form a box joint.