Interlocking sections for forming seating unit for manhole cover
作者： Evans Richard
DOI:
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摘要: The interlocking sections 2,4,6,8, for forming the seating unit to support a manhole cover frame on top of concrete covering slab, are each provided with male 19 and female joint portions enable number be interlocked form unit. preferably mortise joints. abutment surfaces roughened or recessed facilitate engagement mortar. may reinforced.
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