This is an illegal play, as its name suggests. It should attract a severe penalty. The following is an example:
South, the declarer, has to make three tricks in spades. Calling for the ♠J from dummy and receiving a small card from his right-hand opponent, he fails to follow suit. Fourth hand will follow with either the ♠Q or a low card. If low, declarer quickly corrects his revoke by substituting the ♠10. If instead the ♠Q appears, declarer corrects his revoke by producing the ♠K. His left-hand opponent can now change his card but South takes the marked finesse on the next round.
This is one technique not to use.
