What type of mark indicates the edge of a channel?

Lateral marks are specifically designed to indicate the edges of a navigable channel, providing guidance to mariners about which side of the mark they should pass. These marks typically come in pairs—often a red mark on the port side and a green mark on the starboard side, as per international standards. This system helps vessels safely navigate through a channel by showing the proper course to follow, ensuring safe passage while avoiding hazards and shallow areas outside the marked channel.

In contrast, cardinal marks indicate the directions of safe water relative to the mark itself, such as north, east, south, and west. Isolated danger marks signify a specific hazard but do not indicate a channel's edge. Safe water marks indicate that there is navigable water in all directions, often placed at the entry of a channel or marking a fairway, rather than delineating the edges of that channel. Each type of mark serves a specific navigational purpose, with lateral marks being the key indicators of channel boundaries.