In its simplest form, the basic rule for the employment of transfers over an opening bid of 1NT is: with a 5 card or longer heart suit, bid 2D and with a 5 card or longer spade suit, bid 2H.
The 2 D bid is a command to the opener to bid 2H and the 2H bid is a command to the opener to bid 2S.
There are a number of advantages to the use of this scheme which varies somewhat according to the strength of the responding hand. Let us first consider a weak responding hand of 0 to 10 points on which responder would normally make a weak take-out (assuming that RHO passes), e.g.
AT862 Using transfers, responder bids 2H, opener bids 2S as commanded and
T53 responder, who now has a second bite of the cherry, passes. The advantage of this
6 scheme is that the weak hand is dummy and the stronger hand is concealed and the
J852 opening lead is through the weak hand and up to the strength and tennaces in declarer’s hand.
Now consider a responding hand with 10 to 12 points which would be in the game-try zone, i.e. might make game if the opener is maximum and has a fit for responder’s suit but otherwise would not, e.g.
AK862 Responder bids 2H, opener bids 2S and now responder, who has a second chance to
K53 bid, can further describe his hand. For instance, with the hand shown, responder
62 would bid 2N, showing a semi-balanced hand with 5 spades and game-try points.
J85 With 6 spades, responder would bid 3S since there would then be at least 8 spades
between the two hands. Either way, of course, the bidding is still not at an end and
opener will choose between pass, 3S, 3N or 4S.
With a game-going hand the options are even greater, e.g.
a. AK862 b. AK862 c. AK8762 The bidding:
K53 K53 K53 a. 1N – 2H, 2S – 3N
62 6 6 b. 1N – 2H, 2S – 3C
A85 AJ85 A85 c. 1N – 2H, 2S – 4S
It will be noted that when playing transfers, the response of 2S to a 1N opener becomes redundant but rather than let it lie fallow it is usual to give it a conventional meaning. There are many possibilities but the two most popular uses at club level are:
a. a balanced 11 points ( leaving a response of 2N to show precisely 12 points).
b. a transfer to the minors.
Of these two, I personally think that the second is more useful and works like this:
In basic Acol a bid of 2D over 1N is natural and is a weak take-out but when playing transfers the bid of 2D is usurped by the showing of a 5 card heart suit so 2S replaces this lost bid by making it a transfer to diamonds. The down side of this is that a weak take-out into diamonds has to be made at the 3 level.
The normal method of making a weak take-out into clubs is to bid 2C (ostensibly Stayman) and then bidding 3C whatever opener’s response might be. Most people playing transfers abandon this method and instead define 2S as a transfer to clubs. If the responder’s suit is clubs, he passes and if it is diamonds, he simply converts to 3D.