| 摘要 |
PROBLEM TO BE SOLVED: To largely lower the quantity of chaff used, and to make the quantity of chaff smaller than a conventional method, approximately one third or a quarter while transportation cost, packaging cost, labor cost and the like can be reduced largely. SOLUTION: The inside of a net cylinder 1 is filled with a covering material 3 such as chaff as jetting the covering material 3 from the rear-end side of a paper tube 2 while drawing out the front end of the net cylinder 1 installed onto the surface of the paper tube 2 under a compressed state in a bellows shape and constituted in a long-sized cylindrical shape. The net cylinder 1 under a filled state is laid on the top face of a culvert tube 5 piped in a ditch 4 for the culvert.
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