Splinter Bid

A Splinter Bid is an artificial raise of partner's suit which forces to game.

A regular Splinter bid is an unnecessarily high jump bid which promises 4+ of partner's suit plus a singleton or void in the suit bid. For a splinter such as 1 - 4, the splinter shows 13-15/16 points (HCP + dummy points).

With shortness in a suit above opener's, a jump to the 3 level is a splinter, such as 1-3.

The reason for requiring 4+ trump support is that the short suit is of limited value without extra trumps with which to ruff. Take the hand AKQ2 KT9 T A8542 with partner opening 1. While KT9 is excellent trump support, after trumps are drawn, dummy may have none left for ruffing. Playing 2/1 Game Force, instead of splintering, we would bid 2 to set the game force, then bid spades over opener's rebid, and finally raise hearts, which shows the shape.

A Splinter shows enough points for game, but not enough for slam unless partner has a good fit. For an excellent discussion of this, see Adam Parrish's column in the January 2019 issue of Bridge Bulletin, p.45.

Parrish's key point is that if one partner shows shortness in a suit and the other partner has no honors in that suit below an ace, the HCP needed for slam drops from ~33 to ~28. The player who has no wasted values in partner's short suit should usually explore for slam.

Examples:

1	(P)	4	is a Splinter, since a normal weak or strong jump shift would be 1-3. The extra level indicates a Splinter.
1	(P)	4	is not a splinter bid. In the first place, it is a quadruple jump, not a triple jump. In the second place, it goes beyond the level of game in partner's suit. Normally, you do not Splinter if it takes you beyond game level. For example, after 1-(2)-?? you would not make a triple jump to 5 to show a Splinter because it takes you past 4. Yet 4 is normally not played as a splinter either since most people play that a single jump-shift in competition shows either a weak or strong hand (depending upon partnership agreement) though another partnership agreement could make an exception over a preempt by the intervening opponent.
1	(P)	3	is another triple-jump splinter bid.
1	(1)	3	is just a double-jump, but since it is in RHO's suit, it is considered a Splinter A bid of 2 is played by most people as a Cue Bid Limit Raise.

(1)

2

(2)

4   is another 2-level jump Splinter, but this time it is in support of overcaller's clubs.

In the Oct. 2018 Bulletin, p.63, Billy Miller also says that a Splinter should fall in a narrower range of 13-16 dummy points and to use Jacoby 2NT with stronger hands even if you have a singleton.

Mini-Splinter:

Aug. 2023, Bulletin p.41, #6, BidBase with 87 AQ863 T J9842 and partner opening 1, both pairs made a Mini-Splinter to 3.

Splintering by a Passed Hand:

Further to Parrish's point: in the Nov.2010 Bulletin, It's Your Call, hand #4, north is a passed hand and Splinters with 4 after P-(P)-1-(2).

It's a bit unusual for a passed hand to have enough to force partner's 1 opening to game, and should promise other helpful features to make up for lack of HCP.

Alan Falk says that all he needs is for north to have KT754 A5 7 98743 while Colchamiro is hopeful of slam opposite KJ74 AT863 - 8742. So apparently, as little as 7 HCP plus a singleton or void is enough for a passed hand to splinter.

However, Falk also added that such hands are "not enough to Splinter", but happen to fit well with his hand.

If a pair is already in a game force, then a single jump is a Splinter since the usual meanings of a jump-shift normally would not apply. Example: 1-2; 4 is a splinter, not a strong jump-shift.

To Splinter, or Not to Splinter?

In the Jan.2018 Bulletin, p.48, Jerry Helm says that a Splinter bid is more important when it's better to give partner information, and Jacoby 2N is better when you need to get information. WIth the hand 87543 AQ95 5 , you want to know if partner has shortage in spades and should bid 2N to give him a chance to show such shortage, but with KQ743 A952 5 K64, you have the side suits covered, so it's better to let partner know about your shortage.

Bobby Wolff shows the hand AKJ6 K8642 Q652 - with partner opening 1and says:

...a little too much for a splinter which would usually show a minimum raise to game
and having a void rather than a singleton is not ideal. Start with a Jacoby 2NT instead.

However, a Google for Bridge Spinter Bid with void will turn up other experts who say that a splinter shows a singleton or a void.

Opener can Splinter

...with support for responder's suit, a strong enough hand to force to game, and a singleton or void to bid.

Example: 1-1; 3 promises 4+ Hearts, a singleton or void in Spades, and a strong enough hand to make game opposite a minimum, such as with something like x AQxx KQx AKxxx.

Bobby Wolff shows the following hand in his Aces newspaper column of June 6, 2019:

KQ9543 9 A74 AJT  with bidding of  1-1, 2-3 

In Wolff's Nov.5, 2019 column, he shows AKT2 6432 7 AKJ2 opening 1, partner responding 1, and opener bidding 3. Since 2 would be natural and forcing (a reverse), 3 must be a splinter.

In his Jan.26, 2023, with KJ94 AKT964 3 JT and bidding of

(1D) 1H (P) 1S
(P)

In his Feb.22, 2022, Wolff splinters to 4 over partner's 1 with AQJ95 K954 832 8 with only 10 HCP, saying: You have too much playing strength for an invitational raise to 3. He doesn't consider bidding 1 to show that suit and to give opener more room to show his hand, so he must believe that showing the singleton is more imporant than showing the spade suit.

Self-Splinter:

After you open a major and partner bids 1N.

Bobby Wolff shows this hand in his Dec. 12, 2020 Aces newspaper column: AKJ9753 A95 AQ7. After 1-P-1N-P, he says to jump to 4, an auto-splinter self-agreeing spades as trumps with short diamonds and a great hand.

In the Oct. 2022 Bridge Bulletin, p.41, AKQT742 Q32 KT3 is given with the bidding 1-1N (Forcing), followed by 4 which is identified as a Self-Splinter.

After partner has bid a minor which you have not raised, and you have bid a major.

After the bids 1-1;  2, a bid of 2 would be forcing, so 3 can be used as a self-splinter showing a very good 6-card or longer spade suit and game-forcing strength (in light of opener's reverse). Ideally, it would also show 2-3 card support for opener's opening minor, which shouldn't be a problem with 6-1 or 6-0 in the majors.

The same applies to a rebid of the same minor by opener, such as 1-1;  2-3 or -3.

It also applies to a rebid of 1N over your major: 1 - 1, 1N - 4. A bid of 3 may be taken as a strength-showing bid of a second suit. Example: AK8653 A95 - A972, so 4 is a self-splinter.

The bidder of the self-splinter should have bid a major and his partner, a minor, so 1-2; 4 or 1-2; 3 would also be self-splinters, but by opener.

Note that 1-1; 4 would not be a self-splinter but a splinter in support of responder's spades because partner did not bid a minor.

Also note that a single jump to 3 (after 1-1) would be a strong jump-shift, not a splinter. After 1-2, you would be in a game force (playing 2/1 Forcing), though a single jump splinter still takes you to 4. Again, this would be a normal splinter not a self-splinter because partner did not bid a minor..

Likewise, 1-1; 2-3 would not be a self-splinter because the 3 bidder did not first bid a major. It would, however, be a splinter in support of partner's clubs because a simple reverse to 2 would have been strong and forcing.

If playing 2/1 Forcing, the bids 1-2; 2-3 would be a splinter in support of diamonds since you are in a game force, but if not playing 2/1 Forcing, 3 would be strength showing with a heart suit. So a self-splinter would require a jump to 4.

This deal makes slam but may be difficult to reach after 1-2 particularly if not playing 2/1. A simple rebid of 2 indicates a minimum opener of 11-13 HCP. If south has 11 or so, he could well pass. 
If north instead jumps to 3, what can south do? A bid of 4 probably ends things. It's bad bridge for north to ask for aces with a worthless doubleton. A control bid of 5 might do the trick if he can be sure that south will take the bid of south's suit to be a control ask, but it doesn't show his heart shortness. 
Instead of bidding 3, if north makes a self-splinter of 4, the situation should be clear to south who can ask for aces or even make a control bid of 5.

After you have bid (or implied) a suit which partner has raised.

You want to bid slam if partner does not have wasted values in the splintered suit. Good values would be cards headed by a lone ace or by no honors. Honors without an ace, such as KQx, QJTx, etc. are considered "wasted" opposite a singleton or void.

Assuming partner has no wasted values, what should be bid next depends on partnership agreement. You could cue bid the next control, ask for aces, etc. With waste, you would typically sign off by bidding the trump suit at the lowest level.

The Self-Splinter convention requires partnership agreement and discussion.

In summary, the benefit of a self-splinter is that in one bid, you can show your good 6-card suit, your points, and your short suit, as well as implied support of partner's minor.

Rule Of 26 for deciding on slam:

A splinter by responder shows 13-15 HCP. The Rule of 26 says for opener to add his points outside of the splinter suit and if they total 13 or more, a small slam should be on. For example: 1-4 and opener has Kx-AKxxx-QJx-xxx, he has enough to at least explore for slam, but with diamonds and clubs reversed, he would not have enough HCP outside the splinter suit (clubs) because the QJ would be wasted values opposite a singleton or void and thus should not be counted. 

Some specialized Splinters include:

Singleton-Void showing Splinters

Weak-Strong Splinters

Unspecified Singleton-Void Splinters

SpLimit - Splinter Limit Bids