A double-nine set of dominoes is used to build a board of 13x8 squares. (There's also a variant for double-six.) Initially, only the outer tiles are placed, and 13 pawns are lined up on the farthest rank. The goal is to get all pawns into the nearest 2 ranks by placing tiles that permit pawns to cross the board. Pawns are moved orthogonally through a path of pips whose sum is exactly 9. Pawns cannot enter nor pass squares occupied by other pawns.