I made this, I just don't know why

 One of the minor curses of having any sort of shop - at least, if you are the sort who habitually makes problem-solving tools - for any length of time, is that you occasionally find some old tool you've made, and you can't for the life of you remember what it was for.  Well I don't know your life, but it sure makes me feel senile.

 I even went to the trouble of heat-treating this.  I don't even recognize such a shape.  The handle is bent such that it's clearly meant to turn something with that long narrow D shape embedded in it.  I suspect the original shape was an assembly aid for something not expected to ever be disassembled again... yeah, that always makes me break out in hives and then new tools / fixtures.

 And every time I find something like this: "crap! should I save this or not?!?"

 Er, I may have tried to heat-treat it.  The handle part looks suspiciously like the ubiquitous 3/4in x .125 CRS strap I have around.  Good luck putting any hard on that.  I'll check with the sacrificial file when I go back to the shop.

 The Boring Bar Saga isn't over, and there is sad news concerning my lathe, but that's for another, much longer post.