MANHOLE COVER
So here is the answer to the question
WHY ARE SANITARY AND STORM SEWER MANHOLES ROUND?
ANSWER – Because round is the only standard shape that will not fall in on itself. A square shape, or rectangle, or typical triangle, can be turned so that it will fall into the hole. A round sewer cover will not! They are also easier to make.
Tony A. Smith 
Oops! For some reason, I thought you were asking what they are FOR? lol. My goof. Thanks for the interesting tidbit. 🙂
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Hi Tony,
Mmm, I never thought about this until I read your blog. Thanks for answering a question that I would have wondered about! 🙂
Nancy
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