This is a clamp for "Reverse Bowden" setups. It is specifically designed for a "filament roll above the printer" scenario.
Since it is sized for my shelf, you might want to edit the provided .f3d to match your shelf.
I haven't tested how strong the print actually is, but I doubt it would handle overtightening of the screw well, a quarter turn after the screw starts to bite down on the shelf is more than enough.
I suggest printing the clamp's first layer with a single perimeter.
Both files can be printed with no supports in the provided orientation.
The wing with the smaller hole should be upwards. This hole is sized to fit a M6 Pneumatic Fitting for 4mm PTFE tube.
The screw can be tightened to ensure the clamp stays in place.
(Technically not "how I designed this", rather design talk.
This is my first functional project made in Fusion 360. I included a .f3d file for you to edit so it fits your own shelf.