The mounting rail can be placed at the top and bottom position of the front and/or rearpanel. Countersink-holes in the side panel will hold the mounting rails in place. You can also move the mounting rails to any desired position. Just fix the pcbs on the mounting rails with distance bolts or screws. With this mounting rail you can: stabalize the front and/or rearpanel without having visible screws at the front/rearpanel make a "second" frontpanel which is inside the enclosure (like Neve is using it to fix switches) design your own plugin-rack system (for broadcast modules, mic preamps - whatever) make a API500 or 51X compatible rack system fix mechanical parts inside the enclosure
This Version has M3 threads in the mounting rails for M3 screws.
You can also use the mounting rails without the threads, then you need to use the same screws which are used to fix the XLR connectors.