Wednesday, April 20, 2022


Every once in a while, I bite. I can't help it. Curiousity.

One deal shows the little black diamond on a tape measure and says it's going to tell you why it's there. I've never survived all the clicks, gotten past all of the other "facts" (many of them nonsensical), that might be required to find out. I know it has something to do with the center of studs in the wall of a house, but I didn't learn that by hitting clickbait.

Another one is going to tell you why there are holes in the prongs of an electric plug. Hell, I'm a licensed electrician, so I probably should know that. Embarrassingly, I don't. I've hit that clickbait several times, spent endless hours clicking "Next," crashed my computer twice, and I still don't know.

I read comments, so if you know, feel free.


Update, Wed. Apr 20: Aha. I was right; the holes in the electric plug are definitely not to engage a detent in the socket.  Some guy dismantled a bunch of sockets and none of them had any such detents. 


Turns out that, according to the National Electrical Manufacturers Association the holes are "optional, but if present must be located as illustrated above and are for manufacturing purposes." Most plugs are cast, and the holes are for a rod to hold the prongs in position while the material is poured into the die and allowed to solidify.


  1. bruce1:13 PM

    Yeah I've clicked on those too. I figured the diamond had to do with studs, but why the hole in plug prongs? And not every plug has them. Maybe for the electrical gremlins to hide in?

    Oh and the "put a water bottle on your tire" … never figured out that one either.
    Click bait, advertising, web traffic stats, you name it. Useful information? nope.

    Allegedly the hole makes contact with a bump in the socket, to help hold it more firmly.

    The diamonds are for floor joists, I-beam. Or maybe the stud separation for a light load structure, like a shed that doesn't need the standard 16"

  2. I'm going to call bs on the bump in the socket thing. Whatever the holes are there for, that ain't it.

  3. As one who distrusts patriotism in general, there are but a few topics which cause a stirring of nationalistic pride for the UK in me, and our superior 3-pin mains socket is one of them. :union-jack-emoticon:

  4. meh, I dunno about the hole in the prong thing, so I chalk it up to a maybe.

  5. bruce9:19 AM

    okay the "holding in place while casting" makes sense with plastic. Nice trivia sleuthing!