This is an adapter to allow automotive style surface mount switches to be mounted to thicker surfaces such as the 3/4" thick MDF without any router work. It also uses a friction fit so that you can open the box up to service the wiring. The mounting screw holes are 4mm so they will fit most standard 3/4" wood screws without drilling. The main mount hole is 1/2". There is a cutout to allow for a 5mm power in line if needed. if power in is not needed, you may simply align the cut outs away from each to close up the power in hole.