| 摘要 |
The support (3), is provided with a dovetail groove (5) engaged by a bead (4) of substantially the same shape as said groove and forming a portion of the sheet member (2) and substantially rigid in a transverse direction; the groove (5) comprising two longitudinal undercuts (6, 7) engaged by respective longitudinal extensions (14, 15) of said bead (4) and of which one is more pronounced than the other, the sheet member (2) being connected to the bead (4) substantially at the base of the extension (15) engaged in the more pronounced undercut and at a predetermined distance from the other extension (14). |
