To play a higher card from one hand when already winning a trick. You often use this technique when a hand is devoid of entries and the suit is blocked.
For example:
![](https://bernardmageebridge.com/wp-content/uploads/2021/11/image-202.png)
If dummy has no side entry, you overtake the king with the ace. This gives you access to three tricks in the suit and may allow you to run the entire suit if it divides evenly.