There are a number of things that I’ve wondered about off and on for many years. A lot of these have been mentioned on this blog. If you go back several years, you’ll probably find an entry about the same thing that I’ve decided to puzzle over today.
I’m talking about those two holes in all (or most) of the electrical plugs in your house. I’ve always wondered what they were for — it must take some effort to make the holes, so they must have some specific purpose, right?
The number one reason I’ve been given over a lot of years is that they enable the outlet to get a better grip on the plug. I’ve been told that if you look inside an electrical outlet, you’d see that the contact wipers used to transfer electricity to the plug have little “bumps” on them and that these round bits fit snugly into the holes in the plug so the plug won’t fall out of the outlet. Well, I can’t speak for all electrical outlets, but I’ve taken many apart and none of them have little “bumps” that fit into the holes of the electrical plug.
Every time this particular puzzlement of mine pops up, I get about as far as the old “grip” theory and don’t get much further until my mind wanters off to another subject. But today, I thought I’d dig a little deeper….
The first electrical plug in the United States was patented on June 17, 1913 by Harvey Hubbell. Turns out that Hubbell’s design had no holes. His design had little semi-circle indents on both sides of the plug’s prongs. These indents, according to the patent were designed to hook the plug to the socket and prevent it from falling out.
According to my extensive research, a lot of people tried to modify Hubbell’s design and make it their own. “Inventors” came up with plugs with square holes and round holes, but none of them copied Hubbell’s semi-circular indents for fear of being sued for patent infringement. But Hubbell sued them anyway — he lost the case, but all the publicity created a movement that determined, because electricity was becoming so wide-spread, there needed to be a single, universal (standardized) plug in the U.S.
So when all the dust settled, all the designs, including Hubbell’s, converged and resulted in electrical plugs sporting holes in the middle of the prongs and not Hubbell’s semi-circular indents on the sides.
So why are the holes there? In my limited experiment of taking apart electrical outlets, none of them contained anything special to take advantage of an electrical plug’s design, and I couldn’t find anything that fit into the holes of the plug.
Besides the “grip” theory, there are a lot of myths about the “holes.” One such theory is that sometimes manufacturers have important messages they want to convey to their customers about their electrical device and they put that message on a tag that’s attached with a tie-wrap through the holes in the prongs. When you cut or undo that tie, that serves as an acknowledgement that you’ve read the “terms and conditions.” Slipping a zip tie or other material through the holes is also a way to ensure the equipment isn’t being used.
Another theory is that the holes ultimately save the manufacturers money — if you’re mass producing thousands of those little prongs, there’s a lot of metal that comes from those little punch-outs. That metal can be melted down and used to make more plugs….
So — my answer is that those holes do nothing. Maybe people are just so use to seeing the holes, they’d be upset if the plugs didn’t have them. I guess until someone comes up with an explanation that satisfies me, I’ll just continue to ponder….
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