Which term describes the upper edge of a vessel's side?

The term that describes the upper edge of a vessel's side is "Gunwale." The gunwale serves as the topmost part of the sides of a boat or ship, often providing structural support and stability. This part of the vessel can also play a practical role, as it is often used for securing lines and other equipment.

In the context of boating, understanding the components of a vessel is crucial for safety and efficiency. For instance, the gunwale helps to keep water out of the boat, preventing it from swamping and ensuring that passengers remain safe and dry. In contrast, terms like "cleat," "hull," and "beam" refer to different aspects of boat construction and design. A cleat is a device used for securing ropes, a hull is the main body of the boat, and the beam refers to the width of the vessel at its widest point. Understanding these definitions helps in navigating both the physical elements of boating and the terminology used within the boating community.