I have a few switches in my house that for various reasons I don't want people (including myself) to turn them off inadvertently.

This simple clip screws onto the switch plate and can prevent the switch from being turned off or on (depending on whether you install it on the bottom or top position). Leave the screw snug, but not too tight, so the lock can swing to the side when needed to allow the switch to be flipped.

Very simple part...nothing special needed as far as printing goes.