Fourth suit forcing
Bidding the fourth suit doesn't promise cards in that suit, it's just a convenient way to show a good hand and force partner to bid again. This way, you can find out more about partner's hand before settling on the contract. What's that bidding gadget called? You guessed it, "Fourth Suit Forcing."
Bidding the fourth suit is forcing to game and can be a helpful way to start bidding to slam
Here's a hand for you to practice the Fourth Suit Forcing convention.
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Let's take a simple bidding sequence where the opposition are silent.
As South, you hold the hand above. What would you bid next? You have bid your spade suit and could now bid 2♦, your 4 card suit. You could also bid 3NT since you have no interest in partner's heart suit. Your partner seems to have two suits of their own while you have a reasonable holding in the so far unbid diamond suit.
Say you had a slightly different hand but the same bidding sequence.
What would you bid now? Your options might be rather limited. You have enough high card points to bid game, but which game? If partner had a hold in diamonds, you would probably like to be in 3NT. If partner had three card spade support, you would like to be in 4♠.
If partner had neither of the above, you might want to be in 4♥. Your dilemma is that you need to ask partner more about their hand. In fact, you are too strong and have the wrong shape to bid either 3♥ (only 2 hearts) or 3♠ (shows 6+ spades). Without fourth suit forcing, you have to bid 3NT and cross your fingers. Even if partner has a diamond hold, like K5, it is much better they are declarer to prevent the opening leader playing ♦Q squashing the king under the third player's ace.
There is a solution to all this. Play Fourth Suit Forcing. This means that, where you know where you want to play the hand (as in our first example after 2♣), South does not bid 2♦ but bids 3NT. That guarantees a hold in the only unbid suit, in this case diamonds. Where as in our second example, South does not have a hold in the unbid suit, or just requires further information about their partner's hand, they bid the unbid suit. This bid says"tell me more about your hand, partner. What is the most important thing you have not told me yet?"
Criteria for using 4th suit forcing
It only applies when three suits have been bid by your side. If your side has only bid two suits, or the opposition have bid one of the suits, then Fourth Suit Forcing does not apply. No trumps does not count as it is not a suit.
You must have enough high card points to be able to bid game. The "4th suit" bid is forcing your partnership to game. If your partner has for example, shown 11-16 high card points (hcp) and you hold 8 hcp, do not bid the 4th suit. You cannot insist on game as you are not strong enough.
The bid you make being that of the 4th suit must be below 3NT. You are uncertain of the final contract, which game to bid, or maybe whether your partnership has enough hcp to bid slam. So, in our first sequence above, South bids 3NT. In our second, South bids 2♦, Fourth Suit. They need more information.
Responding to 4th Suit Forcing.
What happens when your partner makes a 4th suit forcing bid? What do you bid? The answer is you make the most useful bid you can. Let's look at four South hands after our second sequence and see the choices. Remember our North hand, the same each time.
Bid 3NT. You have a good diamond hold and have already told your partner you have 5 hearts and 4 clubs. Note you showed 5 hearts when you bid 2♣. Had you only 4 hearts and 4 or 5 clubs, you would have opened 1♣.
Bid 2♠, showing three card support for your partner's suit. You cannot bid no trumps with a singleton in the unbid suit. Again, you have already told partner you have 5 hearts and 4 clubs. Hopefully, you and your partner will have at least an 8 card spade fit between you.
You cannot bid no-trumps or support spades. Your partner knows you have 5+ hearts but the one thing they do not know is that you have a fifth club. Therefore, bid 3♣ showing your second suit clubs is a 5 card suit.
You cannot bid no trumps and have no spade support for partner. Your partner knows you have at least 5 hearts and 4 clubs. Help! What do you do? Partner knows everything! Don't pass, ever! The answer is that you rebid your opening suit, 2♥. This may either show a 6th heart (Partner only expects 5) but could also say, as here: "I have nothing else to say, partner. You know my hand shape, roughly, and I can neither support you nor bid no trumps."
So, the normal responses to the 4th suit forcing enquiry are:
- bid no trumps
- support partner
- show extra length in your second suit
- rebid your first suit with none of the above or with extra length in that suit.
Sometimes, you could make more than one of these responses. Then, you must decide which you think would be the most useful for partner.
With the four South hands above, the partnership should finish in 3NT, 4♠, 5♣ and 4♥ respectively. Four different contracts resulting from four different responses to the one 2♦ bid. That is why it is so important that North bids 2♦, 4th Suit, with the above North hand. "Please tell me more about your hand, partner."
There are other things to learn about 4th suit forcing. For now, let's have an example of it in action.
After 2♥, North is too strong to bid 3♦ as that bid shows a long diamond suit, little else and around 10 hcp. So, North checks out for the best game by bidding 3♣, 4th suit. South shows their 5th heart with 3♥ and North raises to game as they have found a fit. 4♥ is the only making game, losing just the ♠A and two club tricks.
One last thing for now. When your partner bids "4th suit", you must alert that bid as the opposition may not understand its unusual meaning. So, go on, try it out. 4th suit to success!