Sequence numbers allow receivers to discard duplicate packets and properly sequence reordered packets. Players must follow suit if able; otherwise may discard any card. They discard the bits of wood, or reuse particles to build partitions between cells. It can discard the contents of all other PIDs. Cards are played by laying them face-up on top of the discard pile. If not, he may discard anything he chooses. In other words, he may not simply discard, if he cannot follow suit. If it continues not to work, discard it and choose another. A concealed meld is one that contains no tiles stolen from another players discard. On SVR4 systems use of may discard data. Players can make a meld by calling for another player's discard. If playing with the discard rule, they must also discard after melding. When done, he must then discard. Solo or not, both opponents may then discard and draw for themselves. The player must then discard a tile, and play continues to the right.