| 摘要 |
The block for covering roofs which are coated with e.g. a layer of bitumen, has rectangular upper and lower faces. The two parallel edges of the block are chamfered through identical angles of 12-23 deg. w.r.t. the vertical. The two remaining edges are vertical. The lower face of the block contains several parallel spaced channels. The upper and lower faces of the block are pref. square whilst the channels pref. run parallel to the chamfered edges. The lower face pref. incorporates a supplementary channel which lies transversely w.r.t. the parallel channels. |
