Why are there holes in the prongs on electrical cords?

Why are there holes in the prongs on electrical cords?
Has anyone ever had an answer to this mystery? Or is is just tradition that goes back to the first electrical plugs, and has no purpose?
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On Tue 24 Jul 2018 12:51:10a, told us...

I have seen people use tiny padlocks with the shackle inserted thru the hole to prevent anyone from plugging them in. Can't think of another reason.
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On Tue, 24 Jul 2018 08:13:58 -0000 (UTC), Wayne Boatwright

There is usually a hardened steel pin in a lock out kit with a ring on the end. You push the pin through the holes in the plug, the lock goes through the ring and between the prongs on the plug.
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On Tue, 24 Jul 2018 08:13:58 -0000 (UTC), Wayne Boatwright

The "divots" are to allow the contacts in the outlet to "grab" the blades of the plug
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On 7/24/18 3:51 AM, snipped-for-privacy@Weiser.com wrote:

https://home.howstuffworks.com/two-flat-prong-plug-holes.htm
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On 7/24/2018 8:07 AM, "\"Retired"@Home.com wrote:

Although I've seen many without hole.
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On Tue, 24 Jul 2018 08:07:00 -0400, "\"Retired"@Home.com wrote in

Thanks.
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On 07/24/2018 02:51 AM, snipped-for-privacy@Weiser.com wrote:

I have one extension cord where the female end can use the holes to hold a male in place.
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On Tuesday, July 24, 2018 at 2:54:18 AM UTC-5, snipped-for-privacy@weiser.com wrote:

Many of the female sockets have a bump-out as part of the material the bade pushes against, and that helps hold the plug into the socket. It is much easier for a manufacturer to make a complete through-hole in the plug eleme nts than to just try to make a partial indent that will engage the bump-out of the socket. For sockets that do not have an integral bump-out, the hol es have no appreciable effect..
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says...

Many years ago they had a purpose. To help hold them in and make good contact. ' That is not the case now and it is just tradition. Some are now not putting the holes in them.
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Still helps clean connections.
Greg
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