I was in need of a side spool mount/holder for my Ender 3 Pro, so I remixed one that I found here on Thingiverse. I've remixed to save material, to become less bulky and more aesthetically pleasing!

Remixed from: https://www.thingiverse.com/thing:4748139

Corrected:
Inserts thickness (piece should now slide easier in the frame);
Inserts height (piece should now be leveled with the printer);
Square nuts holes (height and width, to prevent the nuts from rotating)

This piece is subject to the weight of the filament spool and to mechanical tension, so it should be printed in strong material such as ABS... I printed mine with PLA and it's holding up very well so far, but I compensated my print by setting 30% of infill.

Creality

Ender 3 Pro

No

Yes

Standard

30% Cubic

Nozzle 0.4 at 200º
Glass bed at 50º

4 Layers Top & Bottom
3 Lines Inner & Outer wall

Layer Height 0.2
Line Width 0.4

Speed 60 mm/s
Fan speed 100%