Explanation

Only bishops, rooks, and queens can pin, because these pieces have a long-range attack. If the more valuable piece behind the attacked piece is the king, moving the attacked piece out of the pin is illegal, because putting yourself into check is not allowed. This is an absolute pin, while other pins are called relative pins.

In the first diagram, the bishop is pinning the rook to the king. The rook can’t move, because it would expose the king to check (this is an absolute pin).

In the second diagram, the bishop is pinning the rook to the queen. The rook can move, but if it does, the bishop will be able to capture the queen (this is a relative pin).

In the third diagram, the more valuable piece is in front. The bishop gives check, and when the king moves away, the bishop can capture the rook. This is called a skewer. You will look at skewers in the next lesson.

A pin can often be useful to restrict the mobility of the opponent's pieces. Sometimes a pin can win material immediately. All puzzles in thia level are cases where you can win material with a pin.

Examples

Black can pin the white queen with 1...Rd1.
Now White's queen cannot move "out of the pin", because it would leave White's king in check.
The only legal moves with the queen are 2.Qf1 and 2.Qxd1, in both cases Black can win the queen for the rook.

White can pin the black rook against Black’s queen with 1.Be5.
If Black move's the rook out of the pin, the queen on b8 will be exposed to the bishop's attack.

How to spot a pin

Whenever you can make an attack with a long-range piece, quickly find any pins or skewers by considering what is behind the attacked piece.

Related motifs

An attack on a piece is called a skewer, when moving it out of the attack would expose a piece (of equal or less value) behind it.

The difference between a pin and a skewer is mostly in how the opponent can react to the attack. With a pin, the opponent does not want to, or is not able to move the attacked piece, whereas with a skewer the opponent prefers to move it.

Sometimes a pin does not win material immediately, but because the pin restricts the movement of the pinned piece, additional tactics are possible.
Attacking a pinned piece can win material.
If the pinned piece is protecting another piece, that apparent protection can turn out to be false, and the pin can be used to win material.