by Douglas Creelman This is my second column on right-of-way rules. Last month was about Rule 10 (remember that one?). This month talks about an exception to that rule. When does the Port-Starboard Rule (RRS10) not apply? Well, it does not apply sometimes when boats are approaching an off-wind rounding mark. When boats are in the zone, an inside boat can have mark room even if she is on port tack. The diagram shows what I mean. Two boats are running dead down wind toward a leeward mark, to be left to port. Until they get to the zone, three boat-lengths from the mark, starboard can sail wherever she pleases, and port must yield right of way, as long as she is given room to keep clear. But once either one of them gets within 3 of her boat lengths Rule 18 takes over. Port, as inside overlapped boat, must be given mark room, room to sail to the mark and, when at the mark, to round it in a seamanlike fashion.