Earlier quoted context omitted.
The manhole cover thing was always confusing for me, as where I'm from manholes are all square.
Wonder if people where you're from run into problems where the manhole covers tip onto their diagonal and fall in (since that's the answer I memorized and I think is known as the predominant reason.)
yeah I also memorized that answer, but my follow up question is: storm drain grates[0] seem to be commonly made in a rectangular form, why doesn't the same issue apply there?