I have no idea.
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Probably part of the manufacturing process...
If you would do a Google search, you will find the answer, within 30 seconds, as I did.
If you take apart an outlet, you will see were there are bumps on the contacts that the prongs slide onto. This is meant to hold the plug more firmly and grip the prongs.
@Hot Water posted:If you would do a Google search, you will find the answer, within 30 seconds, as I did.
And if you had taken the extra 5 seconds, as I did (since you searched anyway) you would have provided this link. (or a similar one)
But I guess it made you feel better to criticize without really helping.
-Dave
I am too lazy to do a search. Thanks for the link...lol
@eddie g posted:I have no idea.
The electricity from your wall outlet enters through on of those holes, and out of the other, to complete the circuit.
To accommodate a safety lockout and your outlet detent tabs.
Nice link.... I'll learn something there, but not today 
I was hoping for a reason I didn't know yet.
Note: a loose detent means less pressure on the connection. Pressure has a huge effect for lowering resistance of a connection. A pressured sharp point can easily out do a sq. inch of low pressure. An interesting chart curve
@Lionelski posted:SOME The electricity from your wall outlet enters through on of those holes, and out of the other, to complete the circuit.
"That ain't right"
but you aren't exactly wrong either🤔
Electrons do ride the whole surface, even the hole's. 
"Magic Smoke" comes out of those too 
Holy plugs? is it safe to use unholy ones?
Geez, none of youze guyze know what your're talking about. Those are lightning holes. When lightning strikes your house it travels through the wiring to the blade hole on the left and then exits to ground through the one on the right.
You should never turn the plug around. If you do, the lightning will back up the way it came and start a thunderstorm. Water and electricity don't mix.
Crank
If you put the holes in the cord instead, you may get shocked or start a fire.
And here I thought is was to vent the breeze caused by electricity generated at wind farms...
Rusty
So snarky people have something to snark about when someone asks what they are for. Honestly, if a question irritates you because either a)the person should know it or b)is easily found on google, then don't answer it. This forum isn't exactly a mission critical place where people are discussing things of major importance and any deviation from that wastes precious seconds, it is a board dedicated to what is supposed to be a fun hobby ('model railroading is fun').
More importantly, when people ask "silly questions" it lets the rest of us think of things we likely wouldn't think of, like the what the weird symbols on tape measures are or why we still use the dimensions based on some King's arm length or why Jack Daniels doesn't call itself bourbon (legally, it could)....
"...it is a board dedicated to what is supposed to be a fun hobby ('model railroading is fun')."
Well, i don't know about you, but I'm having a lot of fun this morning reading this thread...just sayin'...
hmmm, detents, you say... I had always assumed that the holes were there for being able to lock-out a cord from being plugged in via a small padlock, etc. Could be both, I suppose. There must be some NEMA code or guide that specifies it - otherwise you wouldn't think the holes would be so ubiquitous... In the meantime, I'm goin' with the lightning theory -- obviously the reason there are upstrokes as well as downstrokes (true) (that's lightning stokes...).
It is a great question and was answered fairly quickly and seriously. However, reading the fake comments has made for a really fun thread and I don't see it reflects on the OP at all. After all, did you you know what they were for before the question was asked?
......."weird symbols on a tape measure" Those symbols all mean something!! 
@Dave45681 posted:And if you had taken the extra 5 seconds, as I did (since you searched anyway) you would have provided this link. (or a similar one)
But I guess it made you feel better to criticize without really helping.
-Dave
Great question Eddie, thanks for the link Dave! And the others for the information!
@Little Giant posted:......."weird symbols on a tape measure" Those symbols all mean something!!
Especially if you measure twice and still cut it too short!
I saw this earlier and was actually interested. I know there was another thread on phasing of transformers and yes I would be interested in understanding why one plug is bigger than the other, which I think relates to the phasing.
I don't get the snarkiness of some of the replies. It's a pretty fair question and I just wonder how you might feel if your question were answered with a how could you be so dumb? I like the forum for all the great help that I can get. Perhaps it's just all that is going around in the world, but some element of kindness isn't such a bad idea.
