Section C
At Marks and Obstructions

Section C rules do not apply  between boats when the mark or obstruction referred to in those rules

is a starting mark surrounded by navigable water or at its anchor line, from the time the boats

are approaching it to start until they have left it astern.

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19 ROOM TO PASS AN OBSTRUCTION
19.1 When Rule 19 Applies
Rule 19 applies between two boats at an obstruction except

when rule 18 applies between them and

(a) the obstruction is the mark , or
(b) the obstruction is another boat overlapped with each of them.
However, at a continuing obstruction, rule 19 always applies
and rule 18 does not.

19.2 Giving Room at an Obstruction

(a) A right-of-way boat may choose to pass an obstruction on

her port or starboard side. If a right-of-way boat changes

course when choosing on which side to pass the obstruction,

she shall give the other boat room to keep clear.

(b) When the boats are overlapped, the outside boat shall give the inside boat room between her and the obstruction, unless she has been unable to do so from the time the overlap began.
(c) While boats are passing a continuing obstruction, if a boat that was clear astern and required to keep clear becomes overlapped between the other boat and the obstruction and, at the moment the overlap begins, there is not room for her to pass between them,
(1) she is not entitled to room under rule 19.2(b), and
(2) while the boats remain overlapped, she shall keep clear and rules 10 and 11 do not apply.

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