When a moored boat must be hove in closer to the dock, it’s a lot easier to grab the bight (the middle) of a rope that’s made fast ashore, then heave up on it while a mate on board holds it with a turn on a cleat. When the boat is significantly shifted, take off the strain quickly while the crew aboard snatches up the slack. Trying to heave the weight in from behind a guardrail is a tough job.