A Splinter Bid is a bid in a side-suit that indicates a trump fit and a singleton or void in the suit bid. For example, a 4 clubs response to a 1 heart opening establishes hearts as trump suit and indicates a singleton or void in clubs. A splinter bid like this is made on hands of such a strength that opposite suitable strong hands that might be held by the partner, a slam in the agreed trump suit is makeable. Whilst taking away a lot of bidding space, splinter bids are very descriptive as they help partner to revaluate his/her hand: soft honors (a king, queen or jack) in the splinter suit lose value, whilst honors in the other three suits gain value.

In some positions if a simple bid of the suit would be forcing then a single jump can be a splinter. For example 1♥, 2♣, 2♦ would be forcing so 1♥, 2♣, 3♦ may be used as a splinter.

The shortage is preferably a small singleton though can occasionally be a singleton honour or a void. The idea is that the partner of the player who splintered can easily tell if he has wasted values in the suit splintered; for example Axxx is ideal where KJ9x is almost worthless.

The 4 diamond bid in the following (undisturbed) bidding sequences are generally agreed to be splinter bids establishing spades as the trump suit:

1♠ - 4♦

1♣ - 1♠
4♦

1♣ - 1♥
1♠ - 4♦

Some partnerships use one of the various forms of mini-splinters to explore for game rather than for slam.