Manhole
From Wikipedia, the free encyclopedia
A manhole or maintenance hole is the top opening to an underground utility vault used to house an access point for making connections or performing maintenance on underground and buried public utility and other services including sewers, telephone, electricity, storm drains and gas. It is protected by a manhole cover, a (usually metal) plug designed to prevent accidental or unauthorized access to the manhole. The reason most manhole covers are circular is that the round cover cannot fall into its own hole (the maximum diagonal distance is the same as the diameter, unlike rectangular covers where the diagonal distance is greater than the maximum length or width).
Manholes are generally found in urban areas, in streets and occasionally under sidewalks.
In rural and undeveloped areas, services such as telephone and electric may be carried on pylons rather than underground.
[edit] Images
 PMG manhole in a city street, Perth, Western Australia. |
 This is a sewer manhole. Typically, only the top ring and manhole cover (not pictured) are visible. |
