Which line is specifically used to prevent a ship from moving forward and aft?

Spring lines are specifically designed to control a ship's movement both forward and aft by providing resistance against motion. When docked, these lines are typically led from the vessel's bow and stern to the wharf or pier at an angle. This tension effectively counters the thrust generated by wind or currents that may push the ship either forward or backward. Their strategic placement allows for greater maneuverability, keeping the vessel more stable in the slip.

Breast lines, while also used in mooring operations, primarily limit lateral movement (sideways) rather than controlling fore-and-aft motion. Mooring lines is a broader term that encompasses any lines used to secure a ship to a berth, which includes spring lines but does not describe their specific function. Guide lines are not standard terminology related to mooring but can refer to lines that help in maneuvering the vessel into position, without addressing the fore-and-aft control specifically.