Low Profile Filament Clip

Where I work, we have a lot of spools laying around. To keep them from unspooling, we usually just thread the filament through one of the holes in the side of the spool. This works but it makes it difficult to stack spools on top of each other. I wanted a way to add a filament clip with a low profile that didn't interfere with normal unspooling while printing and didn't protrude past the side of the spool.

This part was designed to work specifically with the [3Dom USA Eco-Spools](http://ww