This is a box for a relay to remotely switch the printer on or off via i.e. Octoprint. The status of the LEDs show trough, if you print the lowest two layers on the lid in a transparent material.

To mount this box to the printer, I use M4 nuts which catch the printer frame (I have those from a old printer) and M4x6 or M4x8 screws:

The relay this box is designed for is the following. It is often used for Arduino applications and takes 5V power to be controlled. The relay and the lid are mounted with M3x6 screws. To fixate the 220V cable, a longer M3 screw is required.