What is it?
This is a minimalist mount for the Ender 3 for an MKS Gen L v1.0 board to be attached vertically to T nuts on the rail behind the Z motor.
You may find it necessary to re-route some of the wiring in order to reach the connections on the board in this placement. All stock wires are long enough for this application.
4 m4x8 screws
4 m4 T-nuts (drop-in style ideally)
Stock mainboard m3 screws
Heavily inspired by the idea of mounting the board on the outside rail instead of underneath the heated bed - based on mlynch002's design.
I was going to print the one mlynch002 made, but I realized it was a pretty sizable print both in terms of bulk and just the amount of filament needed.
So instead, I took the idea in a minimalist direction since I have a similar setup on my A8, and I've never found myself needing a board fan or anything like that, even with the bed and hotend maxed out at full speed.
0.4mm nozzle / 0.2mm layer
The part is somewhat structural, so I'd probably recommend something like a 20% infill with at least 3-4 perimeters.