Buzz
If you're from the U.S., you're probably well-acquainted with the holes in the prongs of electrical plugs. Most American plugs feature them. But what are these holes actually for?
The reason traces back to the early 1900s when Harvey Hubbell Jr. patented several electrical plug designs, starting with the first detachable electric plug in 1904. Some of Hubbell’s designs included prongs with indents that fit with small bumps inside sockets. When a plug was inserted, the indent-and-bump mechanism helped hold the prongs in place. These indents eventually evolved into holes, which, as HowStuffWorks explains, worked in the same way.
However, this is only part of the story. As various YouTubers have shown, modern outlets usually don’t have bumps anymore—relying on friction and pressure to keep plugs securely in the socket. Nowadays, the holes serve additional purposes. Some manufacturers, like the ones in the video below, pass a rod through all the holes in a series of prongs to secure them while encasing them in plastic.
Cautionary messages can be threaded through the holes, ensuring that consumers notice the warning before using the connected device. Manufacturers might even secure a small lock or zip tie through one or both holes as a form of factory sealing. Another widely held theory is that the holes help reduce metal usage, which can save costs over time.
As per the official regulations from the American National Standards Institute (ANSI) and the National Electrical Manufacturers Association (NEMA), the holes are considered 'optional' and are 'intended solely for manufacturing purposes.' However, if you decide to place a small padlock through one of the plug holes to prevent your children from using certain devices, NEMA likely won't object.
