If another player declares a melded Kong by completing a melded Pung with a fourth similar tile just or previously received from the Wall or the Dead Wall, you may rob the tile, if you can use it to go out. (In classical Chinese rules a player was allowed to rob also a concealed Kong in case the winning tile could be used to complete a special hand Thirteen Orphans. This is not currently supported in Four Winds.)
When you have a chance to rob a Kong, the caption of the Kong command button on the status bar changes to read Rob Kong, and you have five seconds time to response to this clue and click on the Rob Kong button.
Tip: You can have Four Winds notify you of the chance of robbing a Kong by checking the Rob Kong guidance box on the Gameplay option page under the User Interface section in the category tree of the Preferences dialog box.