| 摘要 |
<p>The metal ladder is made up of tubular elements formed out of relatively thin metallic steel strip with a high mechanical resistance. The strip is shaped and opposite strip edges fastened together. Each tube may be fashioned out of one, two or several separate strips, which can be stored on spools. Strips making up an element, particularly those of rectangular (1) cross-section, may be fastened together by folding over the edges (2).</p> |
