This is a power supply cover that allows you to bolt your power supply on top of (or underneath) whatever surface you want. It has more than enough ventilation and doesn't require being bolted into the power supply itself. I recently had a child so the days of exposed mains wiring are behind me.
The included STLs are for a power supply with a width of 114mm and a height of 50mm. It leaves a space of 40mm to make room for the crimped connectors on the back of the power socket/switch and has a wall thickness of 2.4mm.
You can download the F3D files and customize the parameters. The important parameters are PSU width and height, as well as wall thickness.
For the width and height I needed to add roughly 0.5mm to each in order for the cover to fit nicely. I printed in PETG so if you are using a filament that tends to shrink you may want to add a bit more. It's not a big deal if the fit is a bit loose, it will still hold.
I settled on a wall thickness of 2.4mm for my print. Make sure you select a thickness that is a multiple of your nozzle diameter otherwise, at least in my case, cura will try to fill the small gap between the walls with a super-thin line. This caused all kinds of problems on my first print.