About this 3D model
This is a threaded plug (cap) for electrical junction boxes. There are both 1/2-inch and 3/4-inch versions as well as versions that include a hex thumb screw for easy tightening/loosening (which I highly recommend--who wants to carry around a huge flat-head screwdriver just for plugs?). Note: I highly recommend using some dielectric grease on the threads to ensure water can't get into your electrical box. Remember: In order to comply with the National Electrical Code (NEC) you'll have to print this in a flame-retardant filament and protect it from UV rays somehow (either by using UV-stable filament or painting with a UV-protective coating).