A more thorough explanation:

The narrow-channel rule is a navigational requirement that applies to vessels traveling down a narrow fairway. According to this rule, a vessel must keep as close to the fairway wall on its starboard side as is safe and practical.

For example, imagine a large cargo ship traveling down a narrow channel in a busy port. To avoid collisions with other vessels and to stay within the confines of the fairway, the ship's captain must keep the vessel as close to the starboard wall as possible. This allows other vessels to pass safely on the port side and ensures that the cargo ship stays within the designated channel.

The narrow-channel rule is an important safety measure that helps prevent accidents and collisions in busy waterways. By following this rule, vessels can navigate narrow channels with greater ease and avoid potential hazards.