Pressing the Timer Is the Commitment

Pressing the timer while playing a word, exchanging or passing indicates a final choice of move, which may not then be changed (3.4.1(a), 4.1(a)); A player may alter the choice of move at any point before pressing (3.4.1(b), 4.1(b)); Rules cover elements overlapping the opponent's next turn, and ...

Send this to your friend — argument over.