# Why are manhole covers round?

**URL:** <https://boards.straightdope.com/t/why-are-manhole-covers-round/1306>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [March 24, 2000, 11:13pm UTC](https://boards.straightdope.com/t/why-are-manhole-covers-round/1306 "2000-03-24T23:13:00Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![The\_Ryan](https://avatars.discourse-cdn.com/v4/letter/t/7feea3/32.png) [@The\_Ryan](https://boards.straightdope.com/u/The_Ryan)\
**Post date:** [April 18, 2000, 1:40am UTC](https://boards.straightdope.com/t/why-are-manhole-covers-round/1306/21 "2000-04-18T01:40:00Z")

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> [@](#):
>
> One property specifically of the triangular version is that it’s the shape with the minimum area that won’t fall through the hole.

Minimum given what constraints? A dime would have less area than a manhole cover.

Re: rolling puffy shapes  
You guys are confusing rollers with wheels. With a roller, the object is supported at the top of the roller. With a wheel, the object is supported at the middle of the wheel (by the axis). It makes a big difference.

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**Author:** ![shawk](https://avatars.discourse-cdn.com/v4/letter/s/ba8739/32.png) [@shawk](https://boards.straightdope.com/u/shawk)\
**Post date:** [April 18, 2000, 2:56am UTC](https://boards.straightdope.com/t/why-are-manhole-covers-round/1306/22 "2000-04-18T02:56:00Z")

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Some manhole covers in Manhattan are square; some are rectangular; some are round.

I have yet to see a trapazoid or a rhomboid, however.

This is shocking; they call this a city but our manhole cover inventory lacks a complete range of geometrical shapes.

This looks like it’s time for another long letter to the appropriate NYC commissioner.

Dear Sir or Madam;  
I am outraged. You need to take action. …

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