| 摘要 |
A support-strut (3,4) is fixed, directly or by means of an attachment, to the bottom end of each stringer (1,2) of the ladder or scaffolding. The support-strut turns on an axis at right angles to the stringer. The two support-struts intersect each other by means of a cross-piece whose crossing point can be displaced horizontally. The cross-piece consists of a cross-guide (6) movable on a horizontal guide (7).
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