Ender 3 Spool Holder - Side Mounted

Cleaned up and modified the design. Cored out the front and added some ribs to reduce material and add structure.
With 70% infill it's very strong and sturdy.
Check out the original from @cerkit for installation instructions.
I would recommend printing a small piece (about 3-4mm high) to check the fit on your extrusion. It should fit snugly but still be able to slide in from the back of the extrusion behind the Z-motor.