Denied room at the windward mark
The situation
Approaching the windward mark, Finn comes in on the port-tack layline, overlapped inside a starboard-tack boat that is also laying the mark. Finn hails for mark-room as the inside boat, is refused, has to bear away, and protests for being denied his room.
Finn is the inside overlapped boat in the zone — inside boats get mark-room, so refusing it looks like a clear foul by the outside boat.
The question
Inside overlap in the zone usually wins — so why doesn't Finn's?
The ruling
It flips onto Finn. Rule 18 does not apply between boats on opposite tacks on a beat to windward (rule 18.1(a)(1)), so no mark-room exists between them — being inside is irrelevant. It is a plain port-starboard situation under rule 10, and Finn, on port, must keep clear. His demand for room had no basis, and his own protest leaves him penalized. The starboard boat owed him nothing.
Opposite tacks on the beat = no mark-room. The port boat keeps clear under rule 10, mark or no mark.
Opens the situation on the boat-length grid — scrub it and see exactly how the boats meet. Free, no account needed.
Rules cited
See the underlying rule: Rule 18.1 — Port-Tack Layline at the Windward Mark.