Use the tempo gained from the unmasking of the line piece (the threat of TL) to put the masking knight on the same color square as the enemy king and so threaten a zwischenschach.

Here is a great example from the blitz game Kasimdzhanov-Mamedyarov (Kasimdzhanov vs Mamedyarov, 2005), part of their 2005 match.

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White has just blundered by playing 28 ♔h2?. Why is this move a blunder? Because it places the White h2-king on a -dark- square, while the masking Black f5-knight is on a -light- square. Hence the stage is set for a <KNIGHT DISCOVERY ZWISCHENSCHACH>, which Black (Mamedyarov) plays with 28 ... ♘e3!.

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Now if 29 ♖x♕f7, Black plays not the blunder 29 ... ♖x♖f7?? but the <ZWISCHENSCHACH> 29 ... ♘x♕+ and -then- captures the White f7-rook, winning the exchange. After the actual game continuation, 29 ♗x♘e3 ♕x♖f1, Black has still won the exchange.

Event "Blitz Match"
Site "Baku AZE"
Date "2005.11.04"
Round "3"
White "Kasimdzhanov,R"
Black "Mamedyarov,S"
Result "0-1"
WhiteElo "2670"
BlackElo "2674"
EventDate "2005.11.04"

1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Bd6 7. O-O O-O 8. c4 c6 9. Re1 Re8 10. Nc3 Nxc3 11. bxc3 Rxe1+ 12. Qxe1 h6 13. Ne5 Qf6 14. Bd2 Bf5 15. Bf1 Nd7 16. f4 Qe6 17. h3 Bxe5 18. fxe5 dxc4 19. Qg3 b5 20. Be2 Nb6 21. Rf1 Qg6 22. Qh4 Nd5 23. Bh5 Qe6 24. Bxf7+ Qxf7 25. g4 Ne7 26. gxf5 Nxf5 27. Qg4 Rf8 28. Kh2 Ne3 29. Bxe3 Qxf1 30. e6 Qf6 31. h4 Re8 32. d5 Qe5+ 33. Bf4 Qxd5 34. Bxh6 Qd8
0-1