| 摘要 |
The invention relates to a structure which can be folded flat made in a semi-rigid material such as cardboard, having the shape of a cylinder whose directrix is a curvilinear triangle or quadrilateral with its concave face turned outwards. According to the invention, a fold line 7 parallel to the edges 4, 5, 6 is provided in one face 3 which is opposite one of these edges, when the cross section is a triangle, or in two opposite faces in the case of a quadrilateral, so as to allow the said structure to be folded flat. <IMAGE>
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