Abstract: A fastener for anchoring in a hole, formed through a panel structure, by applying the fastener to the hole from one side only, comprises an elongate shank divided longitudinally thereof into two parts, one of which has a portion of uniform, prismatic cross-section along its length and the other of which widens in cross-section towards its free end, said other part has a cross-section so that it is freely insertable into the hole, then the prismatic part is inserted causing the shank to widen on the other side of the panel. The two shank parts may be provided with respective head portions which may be provided at the opposite ends of a clamping strap.