Both sides vulnerable.  
South deals.
                              North
                              S: A Q J 4          
                              H: J 5 2       
                              D: A 8 2       
                              C: A 9 7   
            West                             East
            S: K 9 6 2                       S: 10 7 5 3     
            H: 8 7 3                         H: A 9 6      
            D: 10 6 4                        D: Void              
            C: J 6 3                         C: K Q 10 8 5 2
                              South                         
                              S: 8 
                              H: K Q 10 4   
                              D: K Q J 9 7 5 3
                              C: 4      
          The Bidding:  
                  South    West    North    East                  
                   1D      Pass     1S       2C 
                   2D      Pass     3C      Pass
                   3H      Pass     3NT     Pass
                   4C      Pass     4NT     Pass
                   6D      Pass     Pass    Pass
          Opening lead: 3C
     In 1938, John Gerber of New York City took an idea that was
being developed in Europe and did some work on it resulting in the
Gerber Convention.  This was similar to the Blackwood ace asking
Convention but it used a four club bid as the "trigger".  This
allowed the partnership to determine if it had sufficient
controls for slam at a lower level than Blackwood.
     The problem with the convention is that often a bid of four
clubs was mis-interpreted by partner.  Was it conventional or was
it natural?  The partnership had to discuss this and agree on
some "rules" that they would follow.  There are many variations
but the one I tend to prefer is the "first or last no trump"
approach.  If the first bid in an auction was a no trump bid, or
the last bid in the auction was a no trump bid, then four clubs
was ace asking.
     This worked out well in today's hand.  While South has no 
aces whatsoever, he does have second round control in all four 
suits in a diamond contract.  
     After East inserts a two club bid, North is able to show that
he has a good hand with a club control by bidding three clubs. 
South shows his heart suit and North bids the no trump game. 
     There should be no question that four clubs is the Gerber 
convention.  When partner is able to show three aces, six 
diamonds is virtually a lay down.
     Take the time to discuss Gerber with your partner and be 
sure that you know when four clubs is ace asking and when it is
something else.
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