a modified anchor device for attaching a structure to a thin - walled work piece allows a structure , such as a luggage or utility rack , to be attached to a work piece , such as an automobile roof , without threaded fasteners connecting the structure to the work piece . the anchor device has an double - sectioned head having an upper head member and a lower head member the upper head member extends above the surface of the work piece a sufficient distance such that the upper head member engages the top surface of the structure , thus retaining the bottom side of the structure in face - to - face contact with the top side of the work piece .