| 摘要 |
Two opposite quadratic or rectangular rigid side walls (2, 3) are mutually joined around all side edges by four side walls (4, 5, 6, 7) of which three (eg. 5, 6, 7) are arranged foldably at the centre and the fourth (4) is arranged foldable at the centre or divided along lines (8) which are parallel with the respective side wall connections with the two rigid opposite side walls (2, 3). |
