Abstract: A molded plug is provided that is used to lock structural members together where those members are joined together by the interengagement of a standoff rivet and a keyhole slot. In the normal interengagement of such structural members, a standoff rivet of one of the structural members is inserted into an enlarged portion of a keyhole slot on the other structural member and the structural members are moved relative to each other in order to slide the standoff rivet into the narrowed portion of the keyhole slot. When so positioned, the plug is inserted and locked into position within the enlarged portion of the keyhole slot and thus prevents any relative movement between the structural members to insure that the standoff rivet cannot again become aligned with the enlarged portion of the keyhole slot where inadvertent disengagement of the structural member could occur.