Ossamenta

True, you have to make the grooves first, and then wear will deepen the groove. I'm still not sure how it was used. The grooves are only on one side or two opposing sides, so perhaps something was suspended from it, and after a while they flipped the bone over. But, speaking against this: most double-sided grooves are rather symmetrical in their depth and width. It's so confusing, and yet I know that once I see a picture of one in use, it will be _so_ obvious.