Summary

When I installed the rear support, I noticed that the acrylic frame of the Z-stepper motors was slightly bent forward. So the axle distance of the Z-axis guide was no longer correct.
To get the frame and the guides back into the right position I designed these sockets. I was mainly interested in stability and low space consumption. At the same time I was able to make the play in the hole for the Z-guide rod narrower. I deliberately left the base open at the front in case the Z-motors have to radiate heat.
I couldn't see any influence on the printing result, but the leadscrews are now in the middle of the recesses again.

Printer settings:
Material: PLA
Resolution: 0.2mm
Wall thickness: 1.6mm
Infill: 30-50%
Support: yes