So this load is built with 3 active pcb’s as well as a fourth passive one as a front panel. They are joined with these brass standoffs and I think the standoffs act as circuit paths as well because I see no wires between the different levels. In order to get the alignment right during assembly the designer of these pcbs, made these corners rounded while these ones are diagonally cut and you can see these features along an entire side. This is a neat solution overall because it saves cost and as long as the screws are tight these should provide adequate connection.