Short spacers (or a couple of nuts) are needed to space the module boards off the rails so that there is space for the power wire, and so the PCB tracks on the modules are not shorted. 12mm M3 bolts are adequate with 5mm spacers is the recommended minim combination.
The end mounting bolts and spacers need to be long enough to clear your panel mounted components - 16mm bolts with 10mm spacers is the minimum recommended combination.
Wiring modules to the integral power bus. Each module on the panel is connected like this. The other ends of these wires to the rear of a module's onboard power connector. Power can now be fed to the whole panel through that board's power connector. Power connectors could be omitted from all but one PCB on the panel, although if installed, they are convenient for initial testing of the boards off-panel!
This is a guide only. Parts needed will vary with individual constructor's needs.
Article, art & design copyright 2003 by Ken Stone