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.
Best Answer
This is a ring shank nail they have very good pullout strength , Added for those that don't have 35+ years experience. The Ring shank nails I used in the 70's were 100% except for the tip. No matter how many groves are on the nail it is a Ring Shank nail!. We used them on sub flooring to reduce squeaking and on some kinds of siding where there were big temperature changes that allowed glued sinkers and galvanized to pull out. Added 5/16/16- I did double check with my step dad (retired contractor) and he said they were called ring shank or step shank and there were 2 types but both had the head pulling off issue because of the way they were made. Both of the types 1/2 and double were not legal for long because of the head failure. This is probably why there is not much information on these nails. I remember them because they were so hard to drive straight even with a waffle hammer.