🚀 go-pugleaf

In article <1993Jan5.173440.10482@informix.com> robertw@informix.com (Robert Weinberg) writes:
>Manhole covers are manufactured in circular shape, rather than oval or square,
>to satisfy one paramount condition.

>What is the condition, and why does a circular shape satisfy it?

That they can't fall into their holes, which are the same shape but slightly
smaller.  There's no way to get a diameter of the cover through the hole,
and no matter what orientation you choose you'll have to do that to fall in.

>What other shapes would also satisfy the condition?

At a minimum, any shape of constant diameter.  A non-circular example is the
shape formed by three circular arcs, each of which is 1/3rd of a circle.
(Start with an equilateral triangle, put the points of a compass at two
corners, draw the arc to the other corner; repeat for all three arcs.)

	Howard A. Landman