Kock Werner Redouble

Used after partner's low-level overcall has been doubled, a redouble shows shortness in partner's suit and is takeout for all other suits (including a suit bid by opps already).

For example, if the bidding has gone

Opp Ptr Opp You
1C 1S Dbl Rdbl

The redouble shows a singleton or void in spades and takeout for the other suits, including clubs.