MendelMax and Aluminum Extrusions are awesome to work with. This Y-rod holder is inspired by the ziptie-less LM8UU holders by Jonas Kuehling while also being compatible with MendelMax.
MendelMax v1 had Y-rod holders that spanned two extrusions. v1.5 has a lasercut piece to attach to the center of one extrusion. I like this design but I wanted more play in the length of y-rods that could be used (so I could recycle some from previous bots) and also I wanted a 3D printable version because I can't use wood in my designs (for bioengineering stuff).
Designed in Blender because my OpenSCAD-fu is not very good. .blend file is attached.
You need 2 holders per 3D printer. I use the 4off file because I like to have backups and am building more than one printer :D
These are 10 mm thick, so use M5x16 mm screws to attach to the 2020 Aluminum extrusion instead of the standard M5x10 mm screws. I also print these at 80% infill to make sure they are super rigid. You don't want anything bending or slipping, best to make it super strong because print resolution is linked to the rigidity of your bot.