Lateral Aids to Navigation generally indicate which side of an aid to navigation a vessel should pass when channels are entered from seaward. In the absence of a route leading from seaward, the direction of buoyage, generally follows a clockwise direction around landmasses. The most important characteristic of an aid is its color. The "3R" rule "Red Right Returning" is the rule of thumb for using the lateral system. This means that when entering one body of water from a larger body of water (returning to a harbor), keep the red aids to starboard (right) side and green aids to port (left) side. In addition, each aid is numbered, and these numbers increase as entering from seaward.Preferred Channel Marks are found at junctions of navigable channels and mark wrecks or obstructions. A vessel may normally pass this aid on either side, but the top color band indicates the preferred channel. If the top band of the aid is red, it is treated as a red mark and kept to starboard as the vessel passes it while returning from sea. It may not always be possible to pass on either side of preferred channel aids to navigation.
