Clock is a purely mechanical process with no room for skill, and the chances of winning are exactly 1 in 13.

[5] Some sources give alternative names as Hidden Cards, Four of a Kind and Travellers.

[9] The game is lost if the fourth King is turned up while any cards remain face down.

[10] In a variation of Clock commonly called Watch, players can continue the play when the fourth king appears, by replacing it with a still face-down card.

[12] This gives rules for very different game-play that depends on skill not to miss cards that can be played to the foundations.