Referee's Signal Number 12 - Inadvertant Whistle/Signal
This signal is used by the Referee to indicate that an official has made a mistake and either blown his whistle or made a signal too early, and therefore brought the action to a premature end.
The team in possession may elect to take the result of the play (where the ball was when the signal/whistle occurred) or replay the down.
Begin the motion with your hand made into a fist and held by your armpit, and extend it straight in front of you in an unhurried motion.
If the official concerned has made many of these, a similar signal may be made after the game in the changing-rooms standing immediately in front of that official!