Chess rules( FIDE)
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6.2. When using a chess clock, each player must make a certain number or all moves in an allotted period of time; or may be allocated an additional amount of time after each move. All this must be specified in advance. The time saved by a player during one period is added to his time available for the next period, except in the ' time delay ' mode. In the time delay mode both players receive an alloted ' main thinking time '. They also receive a ' fixed extra time ' for every move. The count down of the main time only commences after the fixed time has expired. Provided the player stops his clock before the expiry of the fixed time, the main thinking time does not change, irrespective of the proportion of the fixed time used.
6.3. Each time display has a ' flag '. Immediately after a flag falls, the requirements of Article 8.1 must be checked.
6.4. The arbiter decides where the chess clock is placed.
6.5. At the time determined for the start of the game the clock of the player who has the white pieces is started.
6.6. The player shall lose the game if he arrives at the chessboard more than one hour after the scheduled start of the session( unless the rules of the competition specify or the arbiter decides otherwise).
6.7.( a) 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 his clock. His move is not considered to have been completed until he has done so, unless the made move ends the game.( See Articles 5.1, 5.2 and 5.3) 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 to keep the 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.
6.8. A flag is considered to have fallen when the arbiter observes the fact or when a valid claim to that effect has been made by either player.
6.9. Except where Articles 5.1, 5.2 and 5.3 apply, if a player does not complete the prescribed number of moves in the allotted time, the game is lost by the player. However, the game is drawn, if the position is such that the opponent cannot checkmate the player by any possible series of legal moves( i. e. by the most unskilled counterplay).
6.10. Every indication given by the clocks is considered to be conclusive in the absence of any evident defect. A chess clock with an evident defect shall be replaced. The arbiter shall use his best judgement when determining the times to be shown on the replacement chess clock.
6.11. If both flags have fallen and it is impossible to establish which flag fell first, the game shall continue.
6.12.( a) If the game needs to be interrupted, the arbiter shall stop the clocks.
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