The fastener has a threaded inner shaft (2) and an outer sleeve (5). The bottom of the shaft has a conical thrust profile to splay the end of the sleeve when the securing nut (17) is tightened on the outside end of the fastener. The bottom of the sleeve has profiled teeth (5,6) and weakened hinge connections (11). The teeth are driven outwards through the interaction with the conical thrust profile and cut into the wall. Each grip segment of the sleeve is displaced outwards in a curve with its centre of curvature outside the fastener and above the grip point. The free end (8) of each grip segment has a sharp profile to cut into the wall.
