| 摘要 |
The manhole cover, comprising a supporting frame (1) and lid (2), has the underside of the lid made with corner blocks which have flat (11A-11D; 12A - 12D) or sloping (13C, 13D) sides to engage with the surfaces of matching recesses (6A - 6D) in the corners of the frame. The corner blocks on one side of the lid are rectangular in shape, while those on the other have sloping surfaces which wedge into the frame recesses.
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