Splinters are a bid that shows a shortage (0 or 1 card) in the splintered suit, and also shows support for partner, in most splinter contexts it should be 4 card support.
When it applies?
The most well known splinter bid applies after 1♥ or 1♠ opening. It is defined as - A double jump after a major opening. The following are double jumps
- 1♥ - 4♣
- 1♠ - 4♦
- 1♥ - 3♠
- 1♠ - 4♥ (This is one to always discuss with partner - I recommend playing it as a splinter but make sure your partner agrees before doing it!).
It is usually a jump to the 4 level, but after opening 1♥, the response of 3♠ should also be a splinter - it is a double jump.
What it shows?
It shows a 4 card raise and approximately 8-11 high card points. Why a maximum of 11? Many people play Jacoby raises or some other form of game forcing raise, with 12+ it is recommended to use that (see Jacoby 2NT: The Game-Forcing Major Raise).
A further requirement that it should have, is that the 8-11 high card points should be sharp cards - typically Aces, Kings, Queen of trumps. There is some leeway, but the majority at least of the hand should be good cards. It should always have 2-3 of these cards.
This is a fine splinter
Example 1
9-11 points, Aces and Kings, a perfect splinter. We don't always get dealt a perfect hand. Lets look at a hand that wouldn't qualify
Example 2
This hand fits in the point range but the cards are too "soft". It has only one King, we need a minimum of 2 but often 3 sharp cards (Aces and Kings).
Note: A splinter should never contain only 3 card trump support.
There are other times splinter style bids apply but they are subject to a lot deeper partnership agreement and are beyond the scope of this article.
How to respond to a splinter
When partner shows a shortage, the best holding you can have opposite that shortage is little or no high card points. This is the basic starting principle for whether to bid slam opposite a splinter - If you have around 16+ high card points OUTSIDE of the splinter suit, slam is likely to be a good shot. You can count an Ace within a splintered suit as 2 points, anything else count as 0. This is one of the most important general principles of bridge bidding - points opposite partners shortage is typically considered to be a misfit.
16 points is a good starting guide, but often more distributional hands require less high card points.
Advantages
Splinters are an excellent bid, most experienced pairs use. In a single bid it shows a lot about a hand, and is very useful when it comes up. Also, it is a good use of the double jump bid which otherwise doesn't have much use - in other words, there is no cost of adding splinters into your system.
Disadvantages
The most common issue is confusion, particularly with the sequence 1♠ - 4♥. People frequently do not know whether partner meant that as natural or as a splinter, and end up in wrong contracts.
Recommendation
I strongly recommend using splinters if you do not already - and also to be fairly disciplined when using them, do not overuse them, follow the requirement of 2-3 sharp cards.
Read next: Best slam bidding conventions · Jacoby 2NT: The Game-Forcing Major Raise · 5NT Pick a Slam: Practical Partnership Agreements · Cue Bids in Bridge: Slam Bidding Made Simple