Rack-Stack is played on a diamond-shaped grid of 16 spaces. Each player has eight pieces in their color. One unusual feature of the game is that the players must pretend that the board is vertical; a piece can only be placed if it is supported on both "lower" sides by other pieces or the board edges. The other unusual feature is that players may play pieces of either color. However, at the end of the game players only score for their own pieces. Scoring is for sets of three pieces at the points of an equilateral triangle. These can be made in three sizes which are worth from one to three points.