This is a box to mount Berker power sockets of the Integro series (others may fit, too) in caravans. They can get screwed on through the back wall and the power cable enters from the lower front to make them installable under seats etc. without wholes in the wall.

I used 4x25 wood screws to mount the box to the wall and 3x16 screws to fix the socket in the box.

The boxes can be printed without support or support starting from print bed (just one little overhang that may need support). I used 10% infill which seems to be stable enough.