A "Kong" is four identical tiles.
There are three ways to make a Kong:
By having three identical tiles on your stake and picking up the 4th tile from any player. If you make a Kong this way it is called an Exposed Kong and it will be placed above your stake for all other players to see. You will notice that one tile at the end of the Exposed Kong is displayed face downwards to indicate that it is an Exposed Kong. The player who makes the Exposed Kong is now dealt a replacement tile and the hand continues from this player.
You can also make a Kong by having three identical tiles on your stake and from having the 4th identical tile dealt to you (this is called a Concealed Kong). If you make a Concealed Kong the tiles will be placed above your stake and you will notice that the tiles at either end of the Concealed Kong are placed face downward to indicate a Concealed Kong. The player who makes the Concealed Kong is now dealt a replacement tile and the hand will continue from this player.
You can turn an Exposed Pung into an Exposed Kong by having the 4th tile that you need to complete the Kong being dealt to you. You cannot pick up a discarded tile from another player to turn an Exposed Pung into an Exposed Kong.
In some exceptional circumstances you can make a Kong to go Mah Jongg - see the section on Special Hands for further information.
There are circumstances when you are not allowed to pick up a discarded tile to make a Kong - this occurs when two or more players want to pick up the same discarded tile. See Precedences for more information.
See also Rules.