Jacob's ladder (nautical)

It consists of vertical ropes or chains supporting horizontal, historically round and wooden, rungs.

A pilot ladder has specific regulations on step size, spacing and the use of spreaders.

This was done to prevent such wooden elements from blocking line of sight or turning into shrapnel when hit by enemy shells.

Although on many ships the only way round was the overhanging futtock shrouds, modern-day tall ships often provide an easier vertical ladder from the ratlines as well.

While they were a popular way of boarding a vessel or carrying out shipside maintenance during the era of wooden ships, and even as recently as the 1950s, their use today on board modern merchant ships is minimal due to obvious safety issues.