A chessclock has two time displays connected so that only one runs at a time (Art. 6.1); Each time display has a "flag"; flag-fall marks the expiry of a player's allotted time (Art. 6.1); A player must press the clock with the same hand used to make the move to complete that move (Art. 6.2.1)
Why people argue about this
People often assume that pressing the clock with either hand is acceptable under Art. 6.2.1 of chessclock rules, but actually, it's crucial to use the same hand as the one used for making a move to complete it correctly and avoid penalties. The confusion arises because this detail isn't always highlighted in explanations or examples provided by FIDE.
