Let’s look at what the rule says:
Rule 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.
Before we delve into the details, let’s remind ourselves what an obstruction is as defined in the rules.
Obstruction An obstruction is
(a) an object that a boat could not pass without changing course substantially, if she were sailing directly towards it and one of her hull lengths from it;
(b) an object that can be safely passed on only one side; or
(c) an object, area or line that is so designated in a rule;
However, a boat racing is not an obstruction to other boats unless they are required to keep clear of her or, if rule 22* applies, avoid her.
(* Rule 22 – Often a capsized dinghy)
In Example 1 below, we see that Blue is not an obstruction to Red because Blue is more than one boat length away, and Red does not need to make a substantial course change.
However, in example 2 we see that Blue is an obstruction to Red because Red is less than a boat length away, Red needs to make a substantial course change, and the other boats are required to keep clear of Red.


Now that we know what an obstruction is, let’s look at some examples of situations where Rule 19 may apply.
Below in example 3, we see two boats approaching the start line. Green is running out of space but Blue is not bearing off. Can Green claim that the start boat is an obstruction?
NO, because the preamble of Part C states that:
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 its anchor line, from the time the boats are approaching it to start until they have left it astern.
Scenario 1
Let’s have a look at the events below. Blue and Green are approaching a channel marker. When it becomes apparent that the channel mark will be an obstruction, Green (the windward boat) decides to leave the channel mark on her starboard side, forcing Blue to bear away. After that, Blue immediately protests, claiming Green broke Rule 11.

YES, Rule 19 aplies
So to sum up Rule 19.1…
- Tells you when Rule 19 applies.
- Applies between two boats at an obstruction.
- Doesn’t apply when Rule 18 applies.