A simple box to put in the middle of an extension cord that safely tucks away the high voltage wiring to a solid state relay for easy control of 120v loads from an arduino or other low voltage source.

print with 2 shells and 100% infill for strength and reliability. adjust size of openings and cord holders on the cap so as to be sure it's a tight fit on your cord to hold it safely. I didn't design in the screw holes on the corners, so you'll have to carefully drill those to hold it together. Or the fit of the cord grips on the cap are pretty tight so that and wrap in tape is probably enough for a temporary install. This is to do some arduino control of halloween decorations :) As with all line voltage experiments, if you're not comfortable doing this sort of thing you probably shouldn't, and if you're too comfortable you might want to review your understanding just to be sure you're properly respecting the death that awaits the uninitiated or their unwitting family members and pets.