Grand Slam Forcing

The simplest version of GSF is simply for partner to bid grand slam with 2 of top three honors, or 6 with fewer than 2.

A more detailed version follows.

This bid asks for top honors in an agreed
trump suit or the last bided suit. If you show
Ace or King and the 5NT bidder bids a relay, the first
step shows the king and the second step the ace.
If Spade is trump:
6C : Ace/King of trump. {6D:relay}
6D : Queen of trump.
6H : 0 top honors & extra length.
6S : No top honors.
6NT: 2 top honors.
7S : All three top honours.

If Heart is trump:
6C : Ace/King of trump. {6D:relay}
6D : Queen of trump.
6H : No top honors.
6NT: 2 top honors.
7H : All three top honors.

If Diamond is trump:
6C : 1 top honor.
6D : Non top honors.
6NT: 2 top honours. v7D : All three top honors.

If Club is trump:
6C : 0/1 honors.
6NT: 2 top honors.
7C : All three top honors.