.....

21  Starting Errors; Taking Penalties; Backing a Sail
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 shall keep clear of a boat not doing so until she is completely on the pre-start side.
21.2  A boat taking a penalty shall keep clear of one that is not.
21.3  A boat moving astern, or sideways to windward, by backing a sail shall keep clear of one that is not.

.....

.....

.....