What is a trial bid?
A trial bid is a bid of a new suit once a suit has already been agreed.
There are several different kinds of trial bid, but the most common asks for help in the new suit bid.
Short Suit Trial Bids
One variety of trial bid is the short suit trial bid. If you agree to play short suit trials then a bid of a new suit once a suit is agreed shows a shortage in that suit and asks partner for length/honours in the suit. Short suit trial bids are most useful when looking for a final contract in no trumps, and will occur only when you have agreed a minor suit.
If you have a major fit then you will play in a major and you probably dont care about shortages as you can trump them.
You also cannot use short suit trial bids after agreeing NT. If you are only interested in game then you do not have time to use a trial bid. In order to agree NT you must be at the 2NT level already. This means that you are going to end up at at least 3NT no matter what
Let’s look at some examples.
North has 19 points and so should open this hand 1 diamond.
South has no suit to bid, but they do have 7 points and diamond support, and so should respond 2 diamonds.
North is now in a bit of a fix. They know they have a diamond fit with partner, but that partner has only 6-9 points. They might only have a combined 25 points, a bit thin for game in a minor. They might consider bidding invitationally in diamonds, but it would be nice to know if no trumps would be a viable contract. North has every suit covered except spades, so they want a way of asking partner if they have some spade cover.
The important thing in this auction is that diamonds have already been agreed. What this means is that North cannot want to bid spades naturally.
Think about it. If south had 4 or 5 of a major then they would have bid that at the 1 level instead of supporting diamonds. On this auction then, it is VERY unlikely that North has opened a minor and received support from partner but then find that they have a major fit too. North would have had to have opened with something like 6 diamonds and 5 spades. If they had a hand this shape with 19 points they may well consider opening 2 clubs.
So once south has supported diamonds, North knows that they will not find a spade fit. They would therefor have no reason to bid spades naturally. So bidding spades here must be artificial.
With a short suit trial bid, bidding 2 spades with the North hand says ‘I have good points and good cover in most suits, but I have a short suit in spades. Have you got any good spade stops partner?’.
Responding to Short Suit Trial Bids
If your partner makes a short suit trial bid then you have a choice of 2 responses. If you have a useful stop in the suit partner is asking about then you should rebid in NT. If you have no useable stop then you should rebid your agreed suit at the lowest available level.
Here is the hand from above. North has made a trial bid in spades.
South has a definite spade stop with the ace and also has the 10 9, which might come in handy!
With spade stops the south hand should bid 2NT, remember they have already shown their 6-9 points.
North now knows that they have at least 25 points between the 2 hands and that South has a good spade stop. They can comfortably bid 3NT.
This time south does not have any useable spade stops. Given this, they should just respond 3 diamonds.
North now knows that no trumps will not be a viable contract here. If south has the upper end of their 6-9 points game might still be on in diamonds. They should then bid 4 diamonds invitationally.
South only has 7 points and a very flat hand, so they should pass.
You cannot use short suit trial bids after agreeing NT.
If you are only interested in game then you do not have time to use a trial bid. In order to agree NT you must be at the 2NT level already. This means that you are going to end up at at least 3NT no matter what partner responds.
Long Suit Trial Bids
A second common type of trial bid is the long suit trial bid. If you agree to play long suit trial bids then bidding a new suit once a suit has been agreed typically shows 3 potential losers in a suit. For example A753 or 532 in a suit.
Long suit trial bids are used when you have agreed a major suit. They can help you to decide whether to bid game or not.
Help in response to a long suit trial bid could be either honours or a shortage.
On this hand North/South agree spades at bid 3. At this point South knows that they have a spade fit and a minimum of 24 points between them. This is a very close call on whether to bid game or not. South might choose to bid 3 spades here, but what they really want to know is if North is going to be able to help with those 3 small clubs.
By bidding 3 clubs instead, south is asking partner if they can help specifically in the club suit.
Responding to Long Suit Trial Bids
Help in response to a long suit trial bid could be either honours or a shortage. Remember that you will be playing this in a trump suit so a short suit will limit your losers by allowing you to trump.
If you can help partner in the suit they are asking about then you should raise to game in the agreed suit. If you cannot help partner then rebid the agreed suit at the lowest possible level.
On this hand North cannot provide any help in the club suit, so they should rebid 3 spades, which will end the auction.
This time North has Ax in clubs, good help for partner. They should therefor raise to game in spades.