When rule 21 or 22 applies between two boats, Section A rules do not

21.1	A boat sailing towards the pre-start side of the starting line or one of its extensions after her starting signal to start or to comply with rule 30.1 keep clear. of a boat not doing so until her hull is completely on the pre-start side.
21.2	A boat taking a penalty shall keep clear of one that is not. WS Case 149
21.3	A boat moving astern, or sideways to windward, through the water by backing a sail shall keep clear of one that is not.