Every <DISCOVERED ATTACK> is a <DISCOVERED PIN> because a <DISCOVERED ATTACK> unmasks an attack by a <LINE PIECE> and <EST - EVERY SINGLE TIME> you are attacked by a <LINE PIECE> you are <PINNED/SKEWERED> to the squares behind you.

Using the masking piece to take what the newly pinned piece no longer defends. Use the masking piece to exploit the pin that is created when this masking piece moves off of the line of the masked line piece(s) behind it.

Discovered attacks which make things pinned are dangerous, dangerous, dangerous.

A complex example of a <DISCOVERED PIN> was played by Rybka Beta (Black) in the following position against Shredder 9:

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First notice the loose h2-square next to the White h1-king, attacked once by the Black g4-knight and defended only by the White h1-king. Loose squares next to your king that the enemy can coordinate on are dangerous!

Can Black coordinate on this loose h2-square, a potential mating focal point? Yes. Black has a b2-rook -and- and his f2-queen all lined up and ready to go to h2 and give mate.

Black needs -only- the b2-rook, the rear piece of the lateral battery, to give mate since the h2-mating focal point is already loose. What is stopping Black from playing 1 ... ♖b2-h2#? Two pieces are stopping this threat by <BLOCKING> the line of attack from the Black b2-rook to the h2-mating focal point, the Black f2-queen and White g2-pawn. The Black f2-queen <MASKS> the Black b2-rook while the White g2-pawn is <PINNED> by the Black b2-rook.

Masking piece, pinned piece, pinned piece, masking. The <DISCOVERED PIN> tactic is ready to go. Rybka played the brilliant 1 ... ♕f3!!, using the masking piece (Black f2-queen) to exploit the <PIN> created by the unmasking of the rear piece (Black b2-rook) by taking what the newly <PINNED> defender (White g2-pawn) only -pretends- to defend (f3-square).

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Now clearly 2 px♕?? runs into 2 ... ♖xh2#, a <PINNING> them. And since Rybka also utilizes the <CLEARANCE> theme by vacating the f2-square to threaten the <SMOTHERED MATE> 2 ... ♘f2#, White simply has too many threats to meet and loses decisive material.