Seaman's Handbook
PART B. Steering and Sailing Rules : Sailing vessels
(a) When two sailing vessels are approaching one another, so as to involve risk of collision,one of them shall keep out of the way of the other as follows:
- when each has the wind on a different side, the vessel which
has the wind on the port
side shall keep out of the way of the other; - when both have the wind on the same side, the vessel which
is to windward shall keep
out of the way of the vessel which is to leeward; - if a vessel with the wind on the port side sees a vessel to
windward and cannot
determine with certainty whether the other vessel has the wind on her port or starboard
side, she shall keep out of the way of the other.