| 摘要 |
A laminar body is prepared from sheets of cardboard and the like by forming an elongated intergral rib in one major face of a first sheet and a corresponding groove in the second major face. A second sheet is fastened adhesively in area contact to the second major face of the first sheet in a position in which the second sheet bounds an elongated duct in the groove. The two sheets, thereby secured to each other, are bent angularly about a line parallel to and adjacent the groove so that the second sheet is on the inside of the resulting bend.
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