| 摘要 |
It basically consists of a frame arranged transversely between the two uprights 1 of the first section of the ladder, capable of rocking on a shaft 7 parallel to the crosspieces 2 thereof and constantly forced to adopt an inclined frontal surface 13-13', forming a slide, over which the crosspieces 4 of the second portion 3 of the ladder act, and an upper surface 11, 11', which is arcuate or non continuous, on which any one of the crosspieces 4 is able to bear, holding the two portions in the relative position required in each case. <IMAGE>
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