# Why do most Edison plugs have 1/8" holes in the blades?



## derekleffew

Almost all NEMA 5-15 and other flat blade devices have a 1/8" hole near the end of the blade. Why? What purpose do the holes serve?


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## rochem

derekleffew said:


> Almost all NEMA 5-15 and other flat blade devices have a 1/8" hole near the end of the blade. Why? What purpose do the holes serve?



I've been told that there are small bumps on the inside of the outlet on the wall. When you plug in the connector, the bumps move into these small holes to help keep it in place. It's not designed to hold really securely, as you can still easily pull it out, just enough to keep it from falling out. I don't know if this is right or not, but it sounded logical when someone explained it to me.


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## Van

rochem said:


> I've been told that there are small bumps on the inside of the outlet on the wall. When you plug in the connector, the bumps move into these small holes to help keep it in place. It's not designed to hold really securely, as you can still easily pull it out, just enough to keep it from falling out. I don't know if this is right or not, but it sounded logical when someone explained it to me.


 This is what I have always assumed but I have never actually checked. Good question.


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## Footer

So you can wrap wires through the holes so you don't have to install and outlet!..... 

Same with Van on this one...


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## willbb123

There are also some extention cords that have a push button lock on them. So the cable won't come unplugged unless you push the button


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## mnfreelancer

There are some lock-out/tag-out products that use the holes as an anchor. I also tag cables that are unsafe with UNSAFE tags and zip ties through these holes.


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## Kelite

mnfreelancer said:


> There are some lock-out/tag-out products that use the holes as an anchor. I also tag cables that are unsafe with UNSAFE tags and zip ties through these holes.




That is a GREAT idea- thanks for mentioning it!


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## porkchop

rochem said:


> I've been told that there are small bumps on the inside of the outlet on the wall. When you plug in the connector, the bumps move into these small holes to help keep it in place. It's not designed to hold really securely, as you can still easily pull it out, just enough to keep it from falling out. I don't know if this is right or not, but it sounded logical when someone explained it to me.



That's what I've always assumed there purpose was


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## gafftaper

Footer said:


> So you can wrap wires through the holes so you don't have to install and outlet!.....



Crap you beat me to it!! 

I think the inside of the socket has a sort of a springy bent piece of metal that squeezes tight and "latches" into that hole.

hmmm even I can't understand what I just wrote.


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## gafftapegreenia

Thats how I've always understood it.

Some prongs don't even have true holes, just recessed areas on the contacts.


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## Chris15

You mean they aren't where you tie your stuff on when using an extension lead as a hauling rope?


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## gafftaper

Chris15 said:


> You mean they aren't where you tie your stuff on when using an extension lead as a hauling rope?



The question wasn't how we ACTUALLY use the little holes... the question is why were they originally designed to be there.


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## jwl868

It’s a vestige from World War II and a result of the War Powers Act to maximize the quantity of basic material for the war effort. To “do their part”, SEAMA (Small Electric Appliance Manufacturers of America) was able to divert tons of brass to the armament industry by this seemingly innocuous modification. The mechanical structure, function, and effectiveness of the plug were unaffected. 

   

Joe


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## Dionysus

The holes are to thwart me!!!
When you are lazy or just can't get behind the desk to unplug something, try to tug on the cable to get it to come out... They just don't want to come out ****it!!!

*shakes fist violently*...

You know that hospital grade (along with some of the other higher grade 5-15 recepticles) actually are required to have stronger spring action to help hold them in. Residential receptacles are not meant to have things often plugged and un-plugged from them.
Had a very BORING discussion on this in one code class.


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