| 摘要 |
A cavity former for forming one or more cavities in a concrete slab, includes a hollow body ( 20 ) about which, during use of the former, poured concrete flows and subsequently cures to form a concrete slab in which the hollow body defines a cavity. The hollow body ( 20 ) has a first wall ( 27 ), a depending skirt wall ( 22 ) about the periphery of the first wall, and structure ( 24 ) defining, within the periphery, at least one depending hollow pillar formation ( 25 ) for in situ bracing the first wall to an underlying surface on which the skirt wall also rests.
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