I needed a way to get power into my dry box and was looking at was to implement this with minimual additional openings to the box.  What started as something only for my dry box, turned into a way to use old C13 style power connectors for computer power supplies, and build them into an extension crd box.  The model is the front and back of the box, that uses #4 wood or metal screws that will self tap into the holes.  there are 4xM3 mounting holes on the back of the box that can be used to mount the box to other things, but if just left stand alone, the bottom two can just be used to mount the C13 connector.  The front of the model will accept a standard wall outlet type fixture and a standard cover plate can go over the front to finish the box.  I used the C13 connector found here:

https://www.amazon.com/dp/B01N2T2N1W/ref=cm_sw_em_r_mt_dp_BJD6KY4FYVCNFZGKM71F?_encoding=UTF8&psc=1

I printed the model with standard settings for PLA at 0.2mm layer height.  Note that if you change the layer height to 0.3, then the inset screw holes may not print correctly, as the floating hole is set for 0.2mm or less layer height.