A Jacobs' ladder is a marine ladder made of rope, or chain with wooden or metal rungs. This is a safety issue because OSHA has guidelines around safe access to board vessels for shipyard workers. Workers must board vessels in drydock, in the water, or from adjacent vessels. Proper access while boarding is critical because many fatalities have occurred from falling into the water or on the surfaces below. When conditions are such that neither a walkway nor a straight ladder can be used to board a vessel, a Jacob's ladder may be used.
Shipyard workers face a hazard of possibly falling from ladders when boarding barges and river towboats because of the movement of the vessel or the ladder. Additionally, structural failure of the ladder causing workers to fall. To mitigate these risks, Jacob's ladders must be of the double-rung or flat-tread type, well maintained, and properly secured. A Jacob's ladder must either hang without slack from its lashings or be pulled up entirely.
For more information on shipyard employment, see this OSHA Shipyard Employment eTool for reference.