Take two two-foot long straps of inch-wide thick black polyester strap. I'm talking about the kind of strap you might find on someone's cheap backpack or gym bag.
Bring each strap around into a circle, so that it overlaps itself by about an inch and a half. Stitch the strap into itself very securely, so that you now have two closed loops.
Now, cut a slit in the stitched part of the loop and thread the opposite end of the other loop through it, tilted at ninety degrees. Stitch that securely as well.
You should have a single entity, a dual loop of nigh-indestructible polyester. The entity is shown here in false colour, one strap in red and the other in blue. Note how the loops at the ends are tilted ninety degrees in relation to each other.
Now you have a copy of the thing I found on the bus.
I still have no idea where it came from, or what it's for.