Changing the next leg of the course and Mark missing

This season’s Notice of Race and Sailing Instructions were thinned down to just 3 pages plus course diagrams. Page 4 was blank so we added some handy rules from RRS Part 3 – Conduct of a race including  33-Changing the next leg of the course and 34-Mark Missing.
Let’s step through those rules and the signals that go with them.
The race committee may change a leg of the course that begins at a rounding mark or at a gate by changing the position of the next mark (or the finishing line) and signalling all boats before they begin the leg. The next mark need not be in position at that time.
(a) If the direction of the leg will be changed, the signal shall be the display of flag C with repetitive sounds and one or both of
    –(1) the new compass bearing or
    –(2) a green triangle for a change to starboard or a red rectangle for a change to port.
(b) If the length of the leg will be changed, the signal shall be the display of flag C with repetitive sounds and a ‘–’ if the length will be decreased or a ‘+’ if it will be increased.
(c) Subsequent legs may be changed without further signalling to maintain the course shape.
The rule book has a section called Race Signals and these signals are also rules. These signals work in conjunction with specific rules.
In summary:
To change the next leg of the course, the Race Committee will display C flag with repeated sound signals before boats begin the new leg. It will also display:
— a red or green signal (a flag or a shape) to indicate if the course has changed to port or starboard, and/or
— a plus “+”  or minus “-” signal to indicate the course length has increased or decreased.
If the leg length is halved and say 10 degrees to port and only a minus “-” and  C Flag were displayed with sounds, a boat is very unlikely to get redress if they have a bad race. In this context the next leg is obvious and not sailing the new leg properly would not be through no fault of her own (sorry about the double negative, but they are the words used in the rules)
What happens next?
The Race Committee can choose to shift the existing mark, in which case it will be the same colour, or it may lay a new mark leaving the old mark in position, perhaps for another division. The new mark will be a different shape or colour to distinguish it.
The Race Committee can then straighten up the course relative to the new leg using existing marks and without any further signals.
What if the Race Committee runs out of marks or correctly coloured marks?
If this happens the Race Committee will try and keep the race alive by using RRS 34 Mark Missing.
If a mark is missing or out of position, the race committee shall, if possible,
    (a) replace it in its correct position or substitute a new one of similar appearance, or
    (b) substitute an object displaying flag M and make repetitive sound signals.
Note: 34 (b) is a very useful rule giving lots of ways to replace or reposition a mark if needed.
As long as an M Flag is displayed  with repetitive sound signals, the Missing Mark can be replaced with any coloured buoy or shape, including a boat!
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