| 摘要 |
Disclosed herein is a ladder assembly consisting of a plurality of ladder segments each comprising a pair of identical rails, a third rail disposed medially between the parallel rails but not in the same plane, a plurality of rungs forming steps perpendicularly positioned and attached to the parallel rails but each diverted medially to attach to the third rail, and a plurality of joints sized to join each segment end-on-end to form the assembly, but with the proviso that in any ladder assembly having at least three segments, one of the third rails in the assembly is shorter than the other rails.
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