What is the term for a two-horned steel fitting used for mooring lines?

The term for a two-horned steel fitting used for mooring lines is "bitts." Bitts are vertical posts usually found on the deck of a ship and serve as anchor points for mooring lines or other cables. They are designed to secure the lines in place under heavy loads, allowing for efficient docking and maneuvering of the vessel. The structure of bitts provides a strong and reliable equilibrium for the tension exerted by the mooring lines, which is critical for safe harboring.

The other options serve different purposes. Cleats, for example, are typically used for tying off lines but have a different shape and are often made of various materials, not exclusively steel. Eyes refer to loops or openings used in line management, and stoppers are used to prevent ropes from slipping through a block or sheave, indicating their specific functions differ from mooring fittings. Thus, bitts are distinctively recognized for their role in the mooring process.