| 摘要 |
<p>The web of the element has transverse slots (1) for attaching fittings and faces outwards. At each longitudinal edge, the metal is folded back on itself before being bent at right angles to the web to form the flanges of the section. This provides an overlap for the edges of the mounting groove in the support and covers any damage made to the edges when the element is inserted. The edges (3) of the flanges are then bent outwards and back on themselves, to form long hooks, which may be toothed if desired. When inserted these hooks provide a firm fixing due to the elasticity of the metal which causes them to grip the sides of the groove.</p> |
