| 摘要 |
A device is disclosed for forming a liquid-permeable flooring, manhole cover or the like with two mutually spaced apart perforated slabs (1, 2) joined to one another by a circumferential wall (3) and which form an intermediate receiving gap (4), the inside diameter of the perforations (5) being substantially smaller in the top slab (1) than in the bottom slab (2). |
