Length tricks are tricks that make by leading a suit when your opponents don’t have any cards left in that suit. Length tricks are dependent on how the suits break. Break refers to how the cards the opponents hold are distributed. If you had 4 spades in your hand and 3 in dummy, the opponents have the remaining 6 spades. Spades break 3-3 if both opponents were initially dealt 3 spades. Let’s look at a mini example:
Here we have 3 sure tricks and if the opponent’s spades break 3-3, we will have a 4th length trick. A 3-3 break occurs 35.5% of the time. Let’s adjust the example slightly.
Here we have the same 3 sure tricks. But now if the opponents spades break 3-2, we will have a 4th length trick. A 3-2 break occurs 67.8% of the time.
Let’s take a look at another example.
Here we have 3 sure tricks, and can make up to two more length tricks. If the opponent’s spades break 2-2 (40.7%) or 3-1 (49.7%) then we will make 3 top tricks and two more length tricks. If one opponent has all 4 outstanding spades, we can still get a length trick. Similar to promotion, we play the 3 top spades, lose a spade, and now the last spade in dummy is top because it is the only one left.
Let’s look at a full deal.
In this hand we need 12 tricks to make our contract (6 + 6). We have 10 sure tricks: 2 spades, 2 hearts, 3 diamonds, and 3 clubs. We don’t have any opportunities for promotion. If we can get 2 length tricks from clubs, we will have our 12 tricks. Win the opening spade lead in dumy and play a low club to the ace. If both players follow, cash 5 club tricks, then your remaining winners for 12 tricks. If one player has all 4 missing clubs, you will go down, but this is a good line that will win over 90% of the time.