| 摘要 |
<p>An adjustable leveling structure for manhole covers, grates and the like within ground and similar structures which comprises an annular-walled ring for supporting a cover, grate and the like near its upper edge and mechanically compressible resilient layer means shaped to conform to the wall of the annular ring and disposed in the space between the outer wall of the annular ring and the ground or similar structure when the annular ring is vertically displaced.</p> |
