This is a box made for 50mm x 26mm 1 channel optocoupler relays. It has guide pins to keep the board from moving inside the box, and slots cut into the ends so that it can be installed inline on a 120/240 power cord. You can then use a Raspberry PI to switch the power on and off using 3 wires with female connector on one end for the PI and male connector for the relay.
There is plenty of room in the box to accommodate cables. Holes or strain relief may be added in a future update to this housing.
Also included is a lid that will accommodate a taller relay board if the wires aren't trimmed well or if you want to put some type of cushion between the board and the relay.
An example of the relay this is built for is https://www.amazon.com/GEREE-Channel-Optocoupler-Level-Module/dp/B00TGTX23I
I am using this in conjunction with Octopi PSU plugin to remotely switch power to a CR-10S printer.