| 摘要 |
A manhole cover comprises a base and a cover. The base has a first inner rim provided with a first bevel while the cover has a second outer rim provided with a second bevel. When the base is joined with the cover, the first bevel of the base and the second bevel of the cover are caused to make contact with each other such that the base is joined with the cover in an airtight and watertight manner. The first bevel of the base and the second bevel of the cover are of such construction that they enable the cover to be lifted easily to set apart from the base.
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