My aunt found a bucket of these things while cleaning out the house. Neither she, my father nor I have any idea what they would be used for. The best way I can describe them is that they look like a cross between a zip tie and a nail.
They are semi-round, with one side being flat but having ridges like a zip tie. The head is slightly rounded and the point is more like a flat-head screw driver tip. The nail is 3 inches in length total. It looks a bit shorter in the image due to camera angle.
The only idea we had for their use would be like some kind of interlocking fastener. One from each side with the ridged edges lining up could create a fairly strong connection.