Wall Switch Lock

Sometimes it's necessary to avoid turning a wall switch on or off. For example, the receptacles in my basement "hobby room" are switched so I can kill power to everything when I'm done for the day. But I want to avoid doing this accidentally if I leave briefly while the computer is running.

This simple tab attaches under one of the screws on a switch wall plate. If attached on the lower screw and rotated upward like this, it prevents the switch from being turned off. On the upper screw and rotated downward, the switch can't be turned on.