Nuttraps for the z threaded rod hit the couplings (box parts on single frame)

[jcrood]

Because the bed's a little lower on single plate builds, the x-axis will descend a little further down than the box build. Depending on the size of the couplings used and the way the extruder/hotend are attached, the nuttraps will hit the couplings before z=0 is reached.

When they're mirrored upside down before printing and then mounted upside down as the original singleplate parts did the nuttraps are at the top of the x-ends, clearing the couplings.

[AxTheB]

I totally agree, I mirrored the x-end parts.