"Darren New" <dne### [at] sanrrcom> wrote in message 
news:484b0f3d$1@news.povray.org...
> Actually, I've never seen anyone get the answer write to "why are 
> manholes round."  I almost hope they ask me that at my next job 
> interview, because the interviewer probably doesn't know either. 
> ;-)
>
> -- 
>   Darren New / San Diego, CA, USA (PST)
>     "That's pretty. Where's that?"
>          "It's the Age of Channelwood."
>     "We should go there on vacation some time."

Round manholes fit whichever orientation you drop them.
Round manholes cover (usually) cyclindrical access spaces which are
better able to resist ground pressures and (again) permit putting 
thiings
into them without concern for orientation. (Round pegs/square 
holes:
square pegs/round holes).

Lots more reasons, but it is a field question as opposed to some
design or theoretical question: what works best and easiest is
what is done.
If you've ever worked with manhole covers you know it is enough 
work
without having to fit corners.

(also - odds are any sufficeintly sized circular manhole cover will 
fit
the odd hole and the odds are that covers with corners will not
work as a --- cover.)

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