> according to the Unicode annotation, it is "a binding signature mark."
I still did not parse what that meant. It is a tad succinct, in that dry way you might expect from a description of Unicode codepoints.
Edit: then it says:
> Binding signature marks are marks placed by publishers on the edges of signatures (aka "gatherings" -- printed and folded sheets in units of 8, 12, 16, 24, or 32 pages) for book binding
