Tiles are always drawn from the top of the next available stack. When only the final stack of 6 tiles remains, the exposed tile is removed from the top of this stack and the other five tiles are drawn in order. The exposed tile (the red 4 in the example diagrams) can never be drawn. When there are no tiles left in the centre except the single exposed tile, if the next player to play does not want to take the previous player's discard, the play ends because there are no cards left to draw.