Rules 18.2(b) and (c) cease to apply when the boat entitled to mark-room has been given that mark-room, or if she passes head to wind or leaves the zone.
If there is a reasonable doubt that a boat obtained or broke an overlap at the time, it shall be presumed that she did not.
If a boat obtained an inside overlap from clear astern or by tacking to windward of the other boat and, from the time the overlap begins, the outside boat has been unable to give mark-room, she is not required to give it.
18.3. Tacking in the Zone
If a boat in the zone of a mark to be left to port passes head to wind from port to starboard tack and is then fetching the mark, she shall not cause a boat that has been on starboard tack since entering the zone to sail above close-hauled to avoid contact and she shall give mark-room if that boat becomes overlapped inside her. When this rule applies between boats, rule 18.2 does not apply between them.
When an inside overlapped right-of-way boat must gybe at a mark to sail her proper course, until she gybes she shall sail not further from the mark than needed to sail that course. Rule 18.4 does not apply at a gate mark.
A boat may hail for room to tack and avoid a boat on the same tack. However, she shall not hail unless
she is approaching an obstruction and will soon need to make a substantial course change to avoid it safely, and
she is sailing close-hauled or above.
In addition, she shall not hail if the obstruction is a mark and a boat that is fetching it would be required to change course as a result of the hail.
After a boat hails, she shall give the hailed boat time to respond.
The hailed boat shall respond even if the hail breaks rule 20.1.
The hailed boat shall respond either by tacking as soon as possible, or by immediately replying "You tack" and then giving the hailing boat room to tack and avoid her.
When the hailed boat responds, the hailing boat shall tack as soon as possible.
From the time a boat hails until she has tacked and avoided the hailed boat, rule 18.2 does not apply between them.
20.3. Passing On a Hail to an Additional Boat
When a boat has been hailed for room to tack and she intends to respond by tacking, she may hail another boat on the same tack for room to tack and avoid her. She may hail even if her hail does not meet the conditions of rule 20.1. Rule 20.2 applies between her and the boat she hails.