Each player has a set of pieces numbered 1 through 6. The object is to knock the pieces of your opponents out of the game while keeping your pieces in the game. Two standard dice are rolled for movement. The number rolled indicates both which pieces may be moved (as they are numbered one through six), and the value on the other die indicates the distance of the move. Each piece can only knock out opposing pieces bearing the same number.

http://www.printgames.net/english/detail_e/knockout.htm