I Didn’t Know That

Q: Why do the prongs on electric plugs have holes in them?

A: One reason is to keep the plug from falling out of the socket because of its weight and that of the cord. Each hole fits loosely over a complementary bump on the contact wiper of the socket, providing extra friction to hold the plug in place. The holes also serve as a safety feature. A padlock inserted through the hole can prevent an electrical appliance from being used. And safety instructions on a tag attached to the hole are more likely to be read by a potential user.