The letter and the marked points. Including single pass plays and with the aid of suicides other strings might be repeatedly captured during cycles. However, the essential part of the board as to repetition consists of the 10 board points. Classes Ko rule sets can be classified into sets of voidness repetition prohibition Progress of a game is threatened to stop if a whole board position is repeated. Thus repetition of board positions are the main means for ko rules.
Applied measures differ greatly.
A set of repetition evaluates the whole board and applies only one rule to it. Simply speaking, a set of prohibition divides board positions into a cyclical part and a non-cyclical part and applies rules to the parts. On the other hand, it may be hard to detect a repetition of the cyclical part due to a great variety of cyclical move-sequences in it. With a played part of a cyclical move-sequence even with use of a set of repetition players will analyse with the aid of a partition rather than referring to the whole board position. A repetition set has a very short text but allowes a high variety within cyclical parts of the board.