Dan Desjardins

so yeah - this was correct. It was a set screw. I figured out I could remove the battery holder and access it with an Allan wrench.   I was able to back it out. Turns out I think it might have ...

When I bought it (on Craigslist) that was my first thought too!  Unfortunately it is inside a box that requires significant disassembly to reach.

Actually if you wouldn't mind measuring if you have one.  The distance from the quarter-20 to the anti-twist nub is right at 15mm on centre.  Would that put the nub inside the semi-circle?

That looks like it will work a treat.  Won't give me the anti-twise, but should accommodate the 'nubbin' nicely.  Ain't eBay great! Thanks Flashlight! Des

Hi: I have a small audio adapter that is supposed to mount to the bottom of a DSLR. Unfortunately it has a small "nub" - apparently there as an anti-twist feature that is not removable.   My D810 ...