A Safety Play is a line of play to reduce the risk of going down in a contract. In that sense it applies to the overall plan of play. Typically, the term Safety Play is used to describe the play in a suit to reduce the risk of a bad break.
Some safety plays give up a potential trick in order to decrease the chance of going down on an unfortunate lie of the cards. Because overtricks are important in matchpoints, these types of safety plays are typically only used in matchpoints when you are in an especially good contract which isn’t likely to be bid at other tables.
Other Safety Plays are simply good bridge, and are applicable in all forms of scoring. Fpr example, with ♠AQ32 opposite ♠7654. You always have at least 3 tricks on a 3-2 break, 3 tricks if the ♠King is onside. You can never win 4 spade tricks. 4-1 breaks are a potential problem. 2 tricks are available if the ♠King is onside. To guard against losing 3 tricks when the ♠King singleton is offside declarer should duck the 1st round of spades or play the ♠Ace on the 1st round. Now declarer can lead low towards the ♠Queen. These lines offer almost a 40% chance for 3 tricks, and almost an 87% chance for 2 tricks.
Some safety plays guarantee you will not lose a trick in the suit. For example if you have ♠KQT92 opposite ♠A854, you have 5 spade tricks on any 2-2 or 3-1 break. You can pickup a 4-0 break either way by beginning with the ♠King or Queen. Now you have a marked finesse if spades break 4-0.
Most Safety Plays involve giving up a potential overtrick to maximize your chance of making your contract. Because of the bonus for making a contract, sacrificing an overtrick to help increase your chance of making your contract is winning bridge.
For example if you have ♠AQ432 opposite ♠8765, a first round finesse against the ♠King offers a 20% chance for 5 spade tricks and better than a 65% chance for 4 spade tricks. If you can afford to lose 1 spade trick, but not 2 spade tricks, you can improve your chances by cashing the ♠Ace first. If the ♠King doesn’t fall, you lead up to your ♠Queen. This Safety Play gives up the chance to win 5 spade tricks, but increases the chance to win 4 spade tricks to almost 72%.
If you have ♦AKQ54 in dummy with no outside entries opposite ♦32, you would play the diamonds from the top if you need 5 diamond tricks. This will work 35.5% of the time. If you only need 4 diamond tricks, you can duck around of diamonds in both hands. This gives up the chance for 5 diamond tricks, but provides almost an 84% chance for 4 diamond tricks.
If you have ♣AJ32 opposite K954, cash the ♣King and finesse against the Queen if you need 4 tricks. This line provides almost a 38% chance for 4 tricks. If you need 3 tricks, you cash the ♣Ace and lead low to the K94, playing the 9 or covering if the 10 or Queen is played. This provides a 100% chance for 3 club tricks.
It is difficult to memorize all the combinations. We recommend counting your winners and losers to determine how many tricks you need. You can then consider what breaks or honor placements you need. If it is possible to guard against a bad break and you can afford to play safely, you should do so using IMP scoring.
For more on Safety Plays, see this article at NorthernColoradoBridge.com.