Abstract: A tack fastener comprising an elongate, tubular body (51), a stem (53) slidable in the body and a compression nut (91) is disclosed. The body (51) has an enlarged threaded hub (55) at one end, which supports the compression nut (91). The other end of the body is slit longitudinally to create a plurality of tangs (57)--preferably four. The tips (61) of the tangs (57) are enlarged and include an inner shoulder (63) that lies orthogonal to the axis of the body (51). The tangs (57) are heat treated to cause them to converge toward one another, resulting in the diameter of the enlarged tang tips (61) being the same or less than the diameter of the main part of the elongate, tubular body (51). When the slidable stem (53) is slid into the body (51), it forces the tangs (57) outwardly, positioning the tang shoulders (63) to impinge on the blind side of parts (105, 107) to be tack fastened together.