Definitions:

1. A ship's ladder with wooden rungs and side ropes. NOUN
   • With the help of my boatmen and my servant I constructed a Jack-ladder, by means of which I scrambled up.
2. An inclined plane up which logs are moved from pond to sawmill typically consisting of a V-shaped trough within which an endless chain carries the logs upwards. NOUN
   • The water pushed logs through a wooden trough to the second jack ladder.

Synonyms:

• jacob's ladder
• pilot ladder