What is a pin in chess?
Updated
A pin is when a bishop, rook or queen attacks a piece that can't move safely, because a more valuable piece stands behind it on the same line. If the piece behind is the king, moving is against the rules. If it is a queen or rook, moving is legal but loses that piece.
Two kinds of pin
A pin to the king is called an absolute pin. You may never make a move that leaves your own king in check, so the pinned piece simply can't leave the line. A pin to any other piece is arelative pin. The piece may move, but the attacker then captures what was behind it.
In the second diagram the rook on f8 could recapture after Bxd8, but Black would still have swapped a queen for a bishop: 9 points for 3.
Only bishops, rooks and queens can pin, because a pin needs a line that runs through one piece to another. A knight jumps, and a pawn or king reaches only the squares next to it.
How a pin wins material
A pin doesn't win anything by itself. It gives you a target that can't run away, or a defender that can't defend.
Attack the pinned piece again
A pinned piece makes a good target, and a pawn is the best attacker because it is worth the least. Here the knight is pinned to the king, so after d5 it can't step aside, and dxc6 comes next.
Take what the pinned piece was guarding
A pinned piece is a poor guard. The f7 pawn seems to protect the knight on g6, but it is pinned to the king by the bishop on c4. White plays Qxg6+, and the pawn is not allowed to take back.
Try it: pin the knight
White to move. Black's knight on c6 and king on e8 share a diagonal. Which piece can reach that diagonal? Tap it, then tap the dot.
Show answer
Bb5 pins the knight to the king. The bishop reaches the diagonal b5 to e8, and the knight on c6 now has no legal move.
How to spot a pin
- Trace the lines from the enemy king and queen. Follow every rank, file and diagonal outward. If you meet exactly one enemy piece, and a bishop, rook or queen of yours could reach that line, you may have a pin.
- Match the piece to the line. Bishops need a diagonal, rooks need a rank or file, and the queen can use either.
- Then look for a second attacker. Once a piece is pinned, ask what else can attack it, starting with your pawns.
- Check your own side as well. Before you rely on a piece to guard something, make sure it isn't pinned.
How to defend against a pin
The simplest defence is prevention: don't leave your king or queen on an open line with one piece in front of it. Once you are pinned, you have four ways out.
- Move the piece behind. In the relative pin above, Qd6 takes the queen off the line, and the knight is free. If the piece behind is the king, step it off the line.
- Block the line. Put a piece between the pinned piece and the piece behind it, as withBd7 below.
- Attack the pinning piece. In the relative pin, h6 attacks the bishop on g5 and forces White to decide straight away.
- Defend the pinned piece. Then capturing it is only a trade, not a free win.
A pin has a close relative with the pieces the other way round: the skewer.
Questions people ask
- Can a pinned piece give check?
- Yes. A piece pinned to its own king can’t move, but it still attacks the same squares, so the enemy king can’t step onto them.
- Can a pinned piece capture the piece pinning it?
- Sometimes. A piece pinned to the king may move along the line of the pin, so a bishop pinned by a bishop can take it. A knight can never do this, because it can’t move along a line.
- What is the difference between a pin and a skewer?
- In a pin, the more valuable piece is behind, so the front piece can’t move. In a skewer, the more valuable piece is in front, so it must move and the piece behind is lost.