Summary

Remix of two things from KeisukeTajima

Using only square connector for connection between the two side of rack
Need: 2 Sides 3 Connector

Connector Square: You can change Y lenght to adjust your need for distance between Sides. (Default: 20cm)
For press-heating fit keep the X and Z lenght, is you want to use glue, lower X and Z by about 5%

Magnet holes as been kept under for stability if used on metal shelf - magnet size: 10 mm diameter x 1 mm thick.