| 摘要 |
<p>One ladder-section consists of two side vertical stringers (a), and four-pieces (c) spaced equally apart. A centre vertical stringer (b) may also be included. Two or more such ladder sections can be fitted together into different shapes: two may be positioned crosswise and flapped together when not in use. The cross-pieces are then bolted together. Alternatively, two ladder-sections can make a V-shape; four can make a square frame. Three make a triangular shaped or H-shaped frame. When assembled, on steep ground, the ends of the cross-pieces are pivot-hinged on both side-stringers or centre stringer.</p> |
