Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:3507331.

Credit /u/pbbft @ reddit for the idea.

Allows loosening/tightening of the coupler at the extruder without a wrench for those times when your filament refuses to go through no matter how you hold your tongue.

Due to variation in printers, it's possible you could need to scale it slightly. The fit should be pretty tight. One side of the hex slot is flared for easier installation (install it from the threaded end). Use a screwdriver, your scraper, or anything that fits the side slot to pry it open a bit as you install it onto the coupler.

GitHub