Abstract: Apparatus for use in joining panel A to panel B to form a corner joint in which panel B has a recess cut in the edge to be joined, the apparatus being in the form of an elongated structural reinforcing and joining member configured in cross-section by a thin rectangular base portion having an inner surface bonded to one surface of panel A, the cross-sectional configuration including an end portion integrally extending from one edge of the base portion and perpendicular the base portion, the inner surface being bonded to an edge of panel A and the cross-sectional configuration being further defined by an integral T portion extending from the base portion in a plane parallel the plane of the end portion, the thickness of the T portion being slightly less than the width of the groove formed in the edge of panel B, the T portion being bonded to the groove in panel B.