Tedm, What rafdav is describing is a safety-device that is used like this:
When you are on the ship and want to be on the shore, you walk along a gangplank that connects the ship to the shore. As you walk on the gangplank, you want to be safe, and want to have a handrail to grab just like you would in a building's-stairwell. The man-rope is a segment of rope that runs the length of the gangplank and is available for you to grab so you can balance yourself as you walk on the gangplank. A man-rope can also be used with a vertical ladder, for the same purpose. The ladder is not the rope-item. The rope is the safety-device that you grab to balance yourself as you climb up or down the ladder.
Here are a couple of examples, even though the Example 1 "gangplank" is between a tree-house and the ground.