If you route something through it, such as a bit of paracord, one of those twist ties used to keep bread fresh, etc. it will lock the knife into the sheath. Useful if you ever need to jump out of an airplane or go through heavy brush or whatnot. I would like to find a tiny carabiner to attach to a belt loop and then through the hole when needed, but I have yet to find one that small.
What I've done on a few of mine is to cut off about 1" of the end of a 16d nail (including the head). Grind down the head a bit so that the shortie nail will fit snugly inside paracord sheath. Core a length of paracord long enough to knot one end through a rivet on the sheath, and insert the nail into the other end, head first. Melt the nail end of the paracord closed.
Now you have a rigid pin that can be inserted through the sheath and talon hole for retention of the knife. When not needed, it can just hang at the side of the sheath. The nail's head creates a bulb in the paracord that won't pass through the talon hole. It's really pretty slick if you get it all fit properly.