This filament guide can be opened up wide or closed down narrow to control the filament.
This was designed to help the spool rotator when it prints large objects (like big vases, etc.):
https://www.printables.com/model/523118-spool-rotator
Print two of the arms and attach them to the clip using 4x20mm hardware, tightened until they are snug and stay put but can still be moved if needed. I put both arms on top and just slid on over the other to close them down.
To install, push the top down onto the top of an Mk3 frame and then push the bottom of the clip over the underside of the frame top.
The author marked this model as their own original creation.