Cracking the books

I unpacked a shipment of books at work today and there was a rubber device of some sort wedged into the front hinge of one. I managed to pry it out without inflicting additional damage to the book. The first thought was it was a suction cup, the sort of thing you stick on a window and dangle a crystal or stained-glass butterfly from. Then something from the distant past surfaced when I saw the bumps on the outside of the thing. "It reminds me of a Spoolie."

I should have taken a picture before I pulled the thingy out but it didn't occur to me.