Which fitting is used to fasten a rope on a boat?

The fitting used to fasten a rope on a boat is a cleat. Cleats are designed specifically for securing lines or ropes, providing a stable and reliable point to tie off when mooring or docking a vessel. They typically feature an elevated shape with two horns or prongs, allowing the rope to be wrapped around and held tightly, preventing it from slipping. This secure method of fastening is crucial for ensuring the safety and stability of the boat while it is at rest or during maneuvering.

In the context of the other choices, while the gunwale is the top edge of the boat's side and plays a role in the structural integrity of the vessel, it is not a fitting for fastening ropes. Similarly, "port" refers to the left side of the boat when facing forward and does not pertain to any type of fastening mechanism. The term "bow" designates the front part of the boat, which is also unrelated to securing lines. Thus, the cleat stands out as the essential component used for fastening a rope on a boat.