T-nut for linear rail mount for 3030 extrusion -

Works for MGN09 and MGN12 rails with hole spacings of 20mm or 25mm.

Insert m3 nuts into the printed parts. The printed part will hold them in the correct place. Of course the nuts normally are too small for the 3030 extrusion and wont hold by them self in place. But the printed part will back the nuts and it worked very well in my tests. Sure you can't screw in the screws with the same torque as into metal slot nuts, but if you use enough screws (every 2nd hole in the rail) the rail will anyways hold well.

They are splitted into half because that makes it easier to be printed on various printers. It also means for a 350mm rail you will need the part 2x. 

At the moment this is only made for 350mm rails  and 3030 extrusions. Shorter or longer rails might work aswell if you cut the print.