 The 1 can be used as the lowest tile, below the 2, or as the highest tile, above the 13, but not both at once.So green 1-2-3 or yellow 12-13-1 would be valid runs, but black 13-1-2 would not be valid.A winning hand consists of 14 tiles formed entirely into sets and runs - for example two sets of 3 and two runs of 4, or a run of 6 plus a run of 3 plus a set of 4.