Pins and skewers

A pin is a line-piece (queen, rook, bishop) attacking through a piece to something more valuable behind it. If the thing behind is the king, the pinned piece cannot legally move. If it is a queen or a rook, it can move, but moving it loses the piece behind, so it might as well be nailed down.

The rule that follows is worth saying plainly: a pinned piece defends nothing. It cannot recapture, it cannot run, and everything it was guarding is loose.

Here White plays 4.d4, hitting e5 a second time. Black's e5 pawn is “defended” by the d6 pawn and the c6 knight, but the knight is pinned. If Black plays a careless move, 5.dxe5 dxe5 6.Qxd8+ Kxd8 7.Bxc6 bxc6 8.Nxe5 and the pawn is gone. Black has to react to the pin now (4...exd4, or 4...Bd7 to break it), and the position is fine. The players who lose the pawn are the ones who counted the knight as a defender.

Two kinds of pin

• Absolute: the piece behind is the king. Moving the pinned piece is illegal. These are the ones that win material by force, because you can pile up on the pinned piece and it cannot leave.
• Relative: the piece behind is a queen or rook. The pinned piece can move, at a price. These are the ones that produce blunders, because the pinned piece looks free.

Breaking a pin

Four ways, in the order you should try them:

1. Block with a less valuable piece (…Bd7 against Bb5).
2. Move the piece behind off the line (castle, or step the king aside).
3. Attack the pinning piece and make it decide (…a6 against Bb5).
4. Ignore it if the pin is doing nothing. Not every pin is a threat, and a bishop that sits on a pin for ten moves is a bishop not doing anything else.

What you should not do is leave a relative pin on the board and forget about it. Those are the games where a rook vanishes on move 30 to a pin that was set up on move 12.

The skewer

Turn the pin around: the valuable piece is in front, the lesser piece behind. Attack the front piece; when it moves, take the one behind.

Skewers are almost always on an open line with a king on it. If your king and a rook or queen share a file or rank with nothing between them and the edge, you are one check away from losing the piece. The fix is cheap: move one of them, or put something in between.

The tell

Any of your pieces standing on a line between an enemy line-piece and your king or queen, or one move from being on such a line. Look for it every time an enemy bishop or rook lands on a long open line. Also: any of your pieces you are counting as a defender. Ask whether it is pinned.

The habit

When you count defenders (the hanging pieces habit), a pinned piece counts as zero. That single adjustment fixes most pin blunders, because the blunder is never “I did not see the pin”. It is “I saw it and still counted the knight”.