capture. It is possible for two opposing pieces to be partially pinning each other. It is also possible for one piece to be pinned in one direction (line of attack) and partially pinned in another, or otherwise pinned in two or more directions. Situational pin Sometimes a piece may be considered to be in a situational pin. A situational pin is not an absolute pin and the pinned piece can still legally be moved; however, moving the pinned piece out of the line of attack can result in some detriment to the player (e.g. checkmate, immediate loss of the game, occupation of a critical square by the opponent, etc.). Consider the diagrammed position, it is White's turn to move. The black bishop on d5 is unprotected and White can capture it with 1.Nxd5; however, White should not play the capture or otherwise move the knight, due to 1...Rb1+ winning White's rook (the king is forced to move, exposing the h1-rook to a skewer attack). It can be said that the white knight is "pinned to the b1-square" rather than pinned to a piece. Pin combinations Pinning can also be used in combination with other tactics. For example, a piece can be pinned to prevent it from moving to attack, or a defending piece can be pinned as part of tactic undermining an opponent's defense. Another tactic which takes advantage of a pin can be called working the pin. In this tactic, other pieces from the pinning piece's side attack the opposing pinned piece. Since the pinned piece cannot move out of the line of attack, the player whose piece is pinned may move other pieces to defend the pinned piece, but the pinning player may yet attack with even more pieces, etc. Using a battery of doubled rooks with a queen behind them to this end is known as Alekhine's gun. A pinned piece can usually no longer be counted on as a defender of another friendly piece (that is out of the pinning line of attack) or as an attacker of an opposing piece (out of the pinning line). A pinned piece can still check the opposing king, however, and therefore can still defend friendly pieces against captures made by the enemy king. Unpinning The act of breaking a pin is unpinning. This can be executed in a number of ways: the piece creating the pin can be captured;