World Chess Federation - FIDE

World Chess Federation - FIDE: "During the game each player, having made his move on the chessboard, shall stop his own clock and start his opponent’s clock. A player must always be allowed to stop hisclock. His move is not considered to have been completed until he has done so, unless the move that was made ends the game. (See the Articles 5.1.a, 5.2.a, 5.2.b, 5.2.c and 9.6)
The time between making the move on the chessboard and stopping his own clock and starting his opponent‘s clock is regarded as part of the time allotted to the player.
b.A player must stop his clock with the same hand as that with which he made his move. It is forbidden for a player to keep his finger on the button or to ‘hover’ over it.
c.The players must handle the chess clock properly. It is forbidden to punch it forcibly, to pick it up or to knock it over. Improper clock handling shall be penalised in accordance with Article 13.4."