Oh, man, now I have to describe the darned thing!
These have been found on horse tack dating to the bronze age. Very simple to make; if you've ever seen the cinch binding on a western saddle, you've seen one.
Bear with me, here. I don't have one in front of me, although I've been making them for a long time.
Stitch two rings into a loop on the end of a strap. The rings will lay along side each other. Take another strap and run over the closest ring to you, down through it, and back between the rings. If you do it correctly you'll be looking at the backside of the strap that you threaded through. Friction holds them in place.
Darn, that sounds wrong. I'll go home and look at one and get back to you tomorrow.
Getting old ain't for sissies!
Moose