In chess, a pin is a potent tactic that involves restricting a defending piece’s movement, which cannot move out of the line of attack of an attacking piece without leaving a more valuable defending piece vulnerable to capture. The act of creating a pin by moving the attacking piece into position is known as pinning, and the restricted defending piece is said to be pinned. Only pieces that can move along a horizontal, vertical, or diagonal line, such as the bishop, rook, or queen, can execute a pinning maneuver. It’s important to note that any piece on the board can be pinned, except for the king.
Basically, there are four types of pins:
An absolute pin refers to a situation in chess where the king is the piece that is shielded by the pinned piece. If a player moves the pinned piece out of the line of attack, their king would be placed in check, which is illegal. Despite being unable to move, a piece that is pinned in this manner can still contribute to the game by giving a check or protecting another piece from capture by the opponent’s king.
This kind of pin is frequently used in the opening stage as well. For instance, have a look at the Nimzo-Indian Defense:
A relative pin is a situation where a piece other than the king is shielded by the pinned piece, usually a more valuable one. While it is legal to move the pinned piece in this scenario, it may not be advisable as it would expose the shielded piece to capture by the opposing player.
And again, a relative pin can be observed in certain openings, e.g. Torre Attack:
A piece that is partially pinned can move and capture along the line of the pin, but it is not allowed to leave that line. This type of pin can occur when a rook or queen is partially pinned along a rank or file, or when a bishop or queen is partially pinned along a diagonal. Even though the pinned piece can capture the pinning piece, it remains partially restricted in its movement. Nevertheless, capturing the pinning piece can still be beneficial for the player who initiated the pin.
You can see a partial pin over the e-file in the position below. Black made a mistake in a defense against the Muzio Gambit, and allowed White to pin the black queen:
At times, a piece can be considered to be in a situational pin. Unlike an absolute pin, in this type of pin, the pinned piece is still legally allowed to be moved. However, moving the pinned piece out of the line of attack can result in some negative consequences for the player, such as checkmate, immediate loss of the game, or occupation of a critical square by the opponent. Essentially, while the pinned piece has some freedom of movement, it is still under considerable pressure and may not be able to move without serious repercussions.
Real game example
As a pin is one of the most common tactical moves, there are literally millions of games that would feature it. Let me present one example that contains multiple pin types in various situations: