I’ve got three switches in my home that pretty much need to be in the “on” position 99% of the time. The consequences of having one of these switches flipped “off” ranges from minor annoyance to zombie apocalypse. One switch goes to our front porch light, one that my laptop is usually plugged into, and the last goes to our wireless router. For a while now I had wanted to create a little cover for the light switch – basically a hollow rectangular tube that would fit over the switch and prevent someone from accidentally flipping it. While I liked the idea, I never got around to actually making it. And then a few days ago I saw Light Switch Lock by Thingiverse citizen Yllonnoce. The design is so simple and elegant that I knew I would be printing it immediately. It permits temporary uses of the switch, all the while discouraging accidental usage. As a result of someone flipping a switch I have literally lost hours of work when my laptop battery ran out of power. Once, as a result of a laptop losing power the hard drive never started up again. So, from now on, this is literally going to be the very first thing I install into any home I live in. At less than 3 grams, each one would probably cost about $0.12 in plastic that will absolutely save me hours of annoyance, frustration, work, and potentially even hundreds of dollars. A simple light switch lock like this could even be used to discouraging the accidental use of a garbage disposal, power tool, or some other appliance. Since these switch locks work upside down, it could even save money by discouraging the accidental flipping of attic or outdoor light switches. Not bad for a $0.12 investment.