Abstract: The fastener can be made of metal or plastic in the form of a semi-flat disc or plate, with some reinforcing ridges if required. The disc or plate can be of various geometric shapes and dimension. At the center of the disc or plate surface is a small hole for inserting an anchoring screw, nail or bolt. On the underside of the disc or plate, vertical projections extend downwardly at angular positions corresponding to 0, 90, 180 and optional 270 degrees with respect to the small hole. The fastener is placed at the intersecting corners formed by abutting edges of rigid insulation boards, arranged in a "stack" or "running" bond pattern. The vertical projections of the fastener insert down into the aforementioned intersecting corners. These vertical projections resist insulation lateral movement or creep after securement of the rigid insulation corner fastener.