I've created this to add MGN12 linear rails onto the D9 500. Since the bed is so big, you're best off with two MGN12 blocks on each rail, to keep it stable - One is simply not stable enough.
You need:
EDIT 26/10-2020:
Following Brian Grimshaws video using my Rail Guides I've updated the description to better explain how to mount them :-)
It will take a bit of fiddling to get the two 4020 extrusions to line up, but it's not at all impossible, and if you measure up distances between extrusions and printer edges, it's pretty quickly overwith :-)
Printer:
Craftbot +
Rafts:
No
Supports:
No
Resolution:
0.2
Infill:
30%
Filament: Generic PETG Grey