If you’ve ever accidently flipped off a light switch connected to the outlet that powers an impossible-to-program electronic or a refrigerator full of food, you’ve probably tried every trick you can think of to prevent it from happening again.

When large warning signs or switches duct-taped in the “on” position fail, try installing a switch lock or guard cover. They make it impossible to flip the switch off—or on, if you’re trying to keep it off.

Installing a switch lock or guard cover on your don’t-touch switch is an easier and more attractive way to protect your important electronics and other must-be-on-all-the-time devices. They cost less than $10.

Some are plastic covers that hide the switch itself to prevent it from being flipped. Others replace the existing faceplate and lock the switch in the on or off position. Some are metal and include a barrier than makes it impossible to flip the switch.

If you’re protecting a switch from kids or still need to use it occasionally, choose a switch lock with an override button you can depress to unlock the switch.