says Tai Bai Yin Jing";
"...construct a chassis out of large timbers and place 6 wheels underneath. On top set a couple of Ya "Teeth" and Gua "Clamps". The ladders are 3.6m long with 4 Zhuo "Rungs" placed 90cm apart, and in shape they are slightly curved so that they pass over one another and clamp into each other. The ladder flies into the clouds and can be used to peer into the city. At the top are a couple of Lu Lu "Pulley Wheels" which rest on the walls as the ladder is extended."
This Cloud Ladder is depicted from a medieval scroll.
An analogous solution to the boarding/escalading problem: an extendable stable platform with a stable access gangway/ladder which is locked onto the target.
from "Chinese Siege Warfare: Mechanical Artillery & Siege Weapons of Antiquity"First Edition (Limited Print)Vol/Issue no.: 160pISBN 981-05-5380-3
See also John Needhams books on ancient asian technology but they cost a bomb.