| 摘要 |
A manhole extension or riser for increasing the height of manhole cover frames when a roadway is resurfaced. It includes roadbed piercing anchors attached to the periphery of a simple ring increasing the height of the frame. The anchors, made of flat steel plates cut into trapezoids, act to lock the riser in place when the new road surface is laid down. A second ring is used to increase the height of the cover support lift.
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