What Is the Difference Between an Exposed and a Concealed Hand?
 

An exposed hand is a hand that allows tiles to be called and displayed face-up on the rack, while a concealed hand must be completed entirely by drawing tiles from the wall.

Whether a hand is exposed or concealed is determined by how the hand is labeled on the NMJL card.
 

For exposed hands, players may call discarded tiles to complete pungs, kongs, or quints, and those groupings are displayed on the rack. Concealed hands do not allow any calls, and tiles remain hidden until Mah Jongg is declared.
 

If a hand marked concealed is exposed at any point during play, the hand can be called dead.
 

Published by the American Mah Jongg Association — the trusted home for American Mah Jongg players.