There are generally two types of turns we are looking for when we barrel. One is what I call a “damaging” turn, the other is an “unchanging” turn, which we discuss below.
A damaging turn takes place when the value of the fourth card renders previous holdings weaker. It is better if this card matches hands that are in your range. These are some examples to get you going, but you can find many more if you simply ask yourself what your opponent is calling with when you bet the flop. The classic one is the ace overcard. If you raise preflop in the small blind, the big blind calls you, you bet a board of 7-5-4 and your opponent calls, it stands to reason that your opponent has many 7-x, 5-x, and 4-x type hands. It’s possible they will fold some of their weak aces, because the board is so coordinated.
If the turn here is an ace that is a very likely card to hit your range. After all, you raised preflop, and preflop raising ranges typically include many aces. It’s also less likely to be in your opponent’s range because your opponent would have reraised preflop with good aces. This card also makes all the flop pairs much smaller. Top pair becomes second pair, second pair becomes third pair, and so on. If he had an open-ended straight draw with a 6 he has now lost equity. More combinations were diminished than assisted with this turn.
Another good example is the one we discussed previously. The board comes
with small connectors, a flush draw, and a high card, such as K♠-6♥-7♥. The
turn is an offsuit middle card, such as J♣. This makes second pair now third pair, and third pair fourth pair. It does not complete any of the numerous flush
and straight draws. The only holding that was unaffected here was the top pair. When your opponent would have raised with a flush draw, a card that brings three to a suit on the board can be the last thing he wants to see. You should lean on this turn as well. The same logic applies to straight draws.
Other overcards are valuable, but broadways cards aren’t nearly as ubiquitous in your raising range. Many people open A-2s from any position but won’t open K-2s on the button. Therefore, when people see a king hit the turn they’re a little less scared than if it were an ace. If you’re going to bet on this turn you should have a good reason, or be prepared to fire again on the river.
The other type of turn is an unchanging turn. These can be very useful, even if they don’t seem to affect anything immediately. If on the K♥-6♥-7♥ board the turn were 2♣ it wouldn’t be as helpful as J♣, but it also doesn’t help 5-4, 8- 9, or any of the numerous flush draws. As discussed earlier, if your opponent is in the habit of calling with ace highs than this card didn’t help him either.
Another even better example can be a board such as K-3-2. You bet on this board and get called. It’s very likely ace highs or even some broadways are calling you as you are likely to miss that board. If the turn here is a 10 or an ace that’s not really good for you. Yes, it’s an overcard to many of the smaller pairs that were calling you, but it still doesn’t make the board scary enough to fold them out. It also gives many draws and pairs to the hand that were floating you.
A better card would be a 2, just a complete blank. It’s very unlikely your opponent has a 2 in his hand, and now none of the numerous combinations of broadways and ace highs have received help. Many people will call with ace high once, but not twice. They’re certainly not calling with broadways again. When you double barrel here you’re more likely to get a number of folds.
Notice how much is predicated on that ace-high call. That is one of the most important statistics or notes you can take down while you’re playing. It’s also great if you know that your opponent’s turn fold-to-continuation-bet statistic is honest, say higher than 55%.