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.