Springy Roll-Up Bookend

This easy-print bookend uses a springy coil to keep your books held up upright. Shoving a new book in pushes the coil out, and it automatically retracts when you remove a book.  I'd seen this sort of thing decades ago, but now, it is kind of a retro thing.

Of course, the one disadvantage of using a plastic coil rather than steel is that over time, it will relax and loose some of its grip. I've found, though, that you can often “rejuvenate” plastic springs by holding them in the coiled position under very warm water (~50 deg C) and then letting it cool before releasing again.

Printing
I recommend printing in PLA. I used a 0.4mm nozzle and 0.2mm layers. You could use a larger nozzle, but make sure that the coil prints with 2 perimeter lines rather than as a single line extrusions.