Remember that when Rule 19.2(b) applies, it never "switches off" any of the rules in Sections A and B. Therefore, in the first diagram if Lou chooses to leave the anchored boat on his starboard side, and if Wendy then passes it on the same side, Rule 19.2(b) requires Lou to give Wendy room between him and the anchored boat, and Rule 11 requires Wendy to keep clear of Lou. If Lou chooses to leave the obstruction on his port side, then Wendy must give Lou room under Rule 19.2(b) and keep clear under Rule 11. This means that Lou may force Wendy as far from the obstruction as he wishes, provided he complies with Rules 16.1 and 17.

In the second diagram, if Susan decides to leave the obstruction to starboard and Paul follows suit, then Susan must give Paul room under Rule 19.2(b) and Paul must keep clear under Rule 10. Note that Paul has an asymmetric chute set and prefers to sail a hot angle to maximize his speed-made-good-to-leeward. However, Rule 19.2(b) does not give him the right to sail at that hot angle while passing between Susan and the obstruction. Susan's only obligation is to give him space to sail between her and the anchored boat in a seamanlike way. Therefore, he may have to bear off to a slower course while passing the obstruction.

If Susan chooses to leave the obstruction to port, then Paul must give her room to do so under Rule 19.2(b) and must keep clear under Rule 10. Susan must comply with Rule 16.1.

Dave Norton

Zack should not risk sailing into the gap between Dave and Carla unless he is confident that Carla will be able to give him room.

The third diagram shows a situation in which Rule 19.2(b) applies at a start. With about a minute to go, a fleet of Lasers is setting up for its start. Everyone has a spot in the front row except Zack, who is hoping he can slip into the front row between Dave and Carla. Here's how the rules apply to Zack. At the position shown in the diagram, Zack must keep clear of Dave and Carla because he is clear astern of both of them (Rule 12). Carla is required by Rule 11 to keep clear of Dave, which she is clearly doing. Dave is an obstruction to Carla and Zack because both of them are required to keep clear of him. When Zack becomes overlapped to leeward of Carla, several things all happen at that moment. (1) Zack acquires right of way over Carla under Rule 11. (2) Zack must initially give Carla room to fulfill her new obligation to keep clear (Rule 15). (3) Carla becomes obligated to keep clear of Zack (Rule 11), and she must also give Zack room between her and Dave under Rule 19.2(b) unless, despite trying to give room from the time the overlap began, she is unable to do so. (5) Zack must continue to keep clear of Dave, first under Rule 12 and after he overlaps Dave under Rule 11. There is one key factor that makes life rough for Zack. Carla has been moving very slowly with her sails luffing, and she is not required to make any effort to fulfill her obligations under Rules 11, 15, and 19.2(b) until Zack actually gets an overlap on her (see ISAF Case 53). Note that last year, some people thought that Dave was a continuing obstruction, but that it not the case this year, as I explained above.