At the regional tournament in Hyannis I picked up this middle-of-the-road 16-count:

♠T983 ♥AK6 ♦Q83 ♣AK7RHO, who dealt, passed. We were playing the standard 15-17 point range for 1NT, so my first bid required little thought.

LHO passed. My partner, who had much more experience than I did, ruminated over her response for a half minute or so. Since almost all 1NT responses are routine, that surprised me a little. I was even more shocked when she reached deep into the bidding box and pulled out the 6NT card. Here is what she held:

♠AKQ ♥95 ♦AKT75 ♣Q43Like most of the players in our direction, we made made seven for 1020. This was about as cold a grand slam, at least in no trump, as you ever see. It works if diamonds split 3-2, if LHO has the J♦, and if either the J♦ or 9♦ is a singleton. There are also squeeze opportunities in three suits.

I remarked at the time that I could think of no tool that would tell her that I had the Q♦. However, halfway through the next hand I realized that we did have such a tool: four-way transfers. Here is how it could have worked:

1. She bids 2NT, which is a transfer to 3♦.
2. I complete the transfer, which tells her that I have at least three diamonds headed by the queen. If I had less, I would bid 3♣ instead. Some people reverse these meanings.
3. She uses Blackwood to determine that I have both missing kings and aces. At the same time my 5♠ response would confirm that I also held the Q♦. After she learned that I had two kings she would know every important card in my hand. 7NT would be a pretty easy bid.

As I said, a minority of teams found it. In fact, a couple of them went down in some contract, probably 7♠.

The moral of the story is that transfers can be used for more than setting the trump suit and right-siding the hand.