While working on creating a stabilization solution for a closed source printer, I decided to use 20x20 based rails but since I didn't want to purchase metal rails, I leveraged a few things to create a construction set.

Current pieces include:

• 20x20 rail (scale Z to desired length)
• 20x20 inner gap fill (scale Z to desired length)
• 20x20 nut (M3)
• 20x20 drop-in nut (M3) - No hex nut needed
• 20x20 nut (M4)
• 20x20 rail connector (M3) (2 nuts with a 5mm bridge)
• 20x20 rail connector (M4) (2 nuts with a 5mm bridge)
• 20x20 rail joiner (connect 2 20x20s to make a 20x40) very tight fit

I've tried to make all the pieces as printer tolerant as possible (adding 0.25mm gaps around all edges). Scaling up should be possible on all of the parts but scaling down gets tricky. I have included the M3 hex blank I used to cut out the holes for the nuts.

All small parts should fit in the printed 20x20 rail snuggly but not tight and should also work in standard extruded 20x20 rail.

To join two rails, I would suggest using 2 rail connectors and 2 gap fillers to provide the best chance of a smooth square join.

I have printed each of these componenets and verified that they all fit when printed on the same printer as long as it has a +/- 0.25mm tolerance.