The power cables of the Geeetech Prusa are very unsafe: only plastic sleeves cover the lead of the 220 V cables and they can slide off easily.
This box fits under the power supply and keeps the offending cables away and safe.
The left screw attachment (in green in the image) is contained in a second STL file so the case can be printed without support. It can be glued to the inside of the case, although it's not necessary: the wall of the case is stuck between the screw and the back of the attachment and can't go anywhere.
I suggest you screw the left screw before you clip the button in or you won't have enough space for a screwdriver.
You'll need a screw slightly longer than the original one.