Described is a fastener having a longitudinal shank designed with a central cross-member; two arms, one at each end of the cross-member; each arm having a forward vane and a rearward vane, the vanes extending longitudinally along at least most of the length of the shank. A flattened head is at one end of the shank, and a pointed end at the other. The head may be notched for ease in collating the fasteners.