The hand is finished when somebody goes Mah Jongg. The complete Mah Jongg hand includes both Exposed sets (displayed above a player's stake) and Concealed tiles (kept on a player's stake). The tiles in the Mah Jongg hand will (with exceptions - see Special Hands for further information), consist of:
Four sets of either a Kong, Pung or a Chow, and a pair of identical tiles.
As soon as a player completes his or her hand they would normally call out "Mah Jongg" and all players Expose their hands ready for scoring. The player who goes Mah Jongg does not discard the final tile that they used in order to go Mah Jongg. Thus 14 tiles are needed to go Mah Jongg.
See also Rules.