Quite silly isn't it?
I have knitting stitch markers that just slide over the needle, but they don't really work when you're crocheting.
I saw a picture of some crochet work with what looked like a lobster claw clasp and some beads used as a stitch marker and it clicked. Hey, I have a bunch of those lobster claws in my jewelry findings. Out came the beads, findings and jewelry pliers and voila!
I made 2 different sizes in black and copper. They are really quite simple to make, just a lobster claw clasp, a head pin and some beads.
And here we are, a much better way to mark crochet rounds.