Welcome to brain Stuff from house stuff works dot com where smart happens. Hi Am Marshall Brain with today's question, why do the two flat prongs on plugs for most electrical appliances have holes in them? If you unplug any appliance in your house, there's a nine percent chance that the two flat prongs have holes in them. There are three reasons for those holes. First, if you were to take a part in outlet and look at the contact wipers that those prongs slide into, you would find that
they have bumps on them. These bumps fit into the holes so that the outlet can grip the plugs prongs more firmly. This detenting prevents the plug from slipping out of the socket due to the weight of the plug in the cord. It also improves the contact between the plug and the outlet. Second, electrical devices can be factory sealed or locked out by the manufacturer or owner using a plastic tie or a small padlock that runs through
one or both of those prong holes. For example, a manufacturer might apply a plastic band through the hole and attach a tag to it that says you must do blah blah blah before plugging in this device. The user can't plug in the device without removing the tags, so the user is sure to see the instructions. Third, there's also a small savings and raw materials for the manufacturer
of the actual plug prong. Every little bit helps. It's been reported that really old outlets used captive ball bearings in coil springs for the detent, but today it's done with a bump on a springy copper contact. Do you have any ideas or suggestions for this podcast? If so, please send me an email at podcast at how stuff
works dot com. For more on this and thousands of other topics, go to how stuff works dot com and be sure to check out the brain stuff blog on the house stuff works dot com home page two