| 摘要 |
The first rail-section (12) has a channel portion (16) whose two arms (20) have edges (22) bent back on the outside. The second one is of inverted-channel section, with edges (30) bent back inwards so as to fit inside those of the first one. Each rail-section has, at each side, two contact areas (34,38) along which they travel on each other in a straight line, leaving no free movement. The contact areas can be symmetrically situated and formed by arched portions (32,34) on the arms of the rail sections. |
