This is a casing for a built-in mains wall socket that can be found in most mainland European countries. I had such a socket lying around but needed a box to mount it on the wall instead of in the wall.

You basically have two options: Either you print the full box "Mains Box Full", but then you need support for the rims. Or you print the "Main Box" and the "Box Rim" separately. You can then glue that on but in my case it had a tight fit with the socket so I could screw it all together.

I know there are tons of different sockets out there. Therefore I have included the sources. Use them or be inspired to create one for your own type of socket.