A filler piece I added to a PETG sheet earlier in the year. Its purpose is to mark a page within a book you reference often. The original one I made grabbed the paper to the point you had to be careful not to rip the paper taking it off. I went ahead and included a revision that uses a larger gap between the front and back; hopefully giving it less of a grab.
Free File Friday #5
The older showroom version with more pics can be found here http://www.ponoko.com/showroom/ShoppingZen/cornermarks-3089