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I've always wondered but never thought to ask: what are these abstract paper patterns on some Jewish seforim? As the two books in bottom center of example photo: http://1.bp.blogspot.com/-jbhcKUqaVsA/VpVGyNLtKJI/AAAAAAAADmY/OP3pRyfWq2g/s1600/19.jpg
It sort of looks like camoflouge, but in red hues. Yes I know it's almost Purim, but don't giggle. I'm seriously wondering this.
You will find this most often on the really "serious" seforim that are all-Hebrew, come from the ultra orthodox people in Israel. Kaftor siddurim have them for example.
Do they mean anything? (Like, is this sort of analogous to the "barcode" of the pre-WWII tallits?) Or is this just a way to make the books appear mehudar (beautified, superior)? To me, it's always just seemed kind of...odd. I don't understand what it has ever done to beautify or enhance or elevate the sefer it is found on.