Whoever designed this didn't give actual wiring any thought. The on/off switch and power inlet are both *inside* the heatsink. While there are holes inside the heatsink fins to (presumably) run wires from the inlet to the switch, there is no way to actually yse that routing. You will need to drill a lot of holes to run the mains cables inside the chassis, out to the switch and back inside. Getting the inlet and switch back in the provided 'space' with actual cables attached to it is a royal pain in the a$$.
Too bad... with a little extra thought (and actually a simpler execution) this chassis could have been practical. Now it's a source of frustration.