| 摘要 |
Openings (7) edge-bounded across the strip (S) are arranged in the center part of the strip at corrugation pitch (W). The openings are parted by webs (8) transverse to the run of the strip (S), the clear width (z) of the openings to be at least of web width (8). The edges (7) of the openings (7) are connected e.g. glued, welded or stitched to one another, preferably at their abutments. The stretch capacity of the main edges (3) is governed by the spacing of the opening edges, opposing edges to run parallel and joined at acute angle of their ends. Where they join, the edges of the openings (7) form ridge vents or venting valves.
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