Castling is a special move in chess that uses both a rook and the king. In castling, the king is moved two squares toward the rook, and the rook moves past the king to the square right next to where the king has moved. Castling takes one move, and is the only way for a player to move two of his own pieces on the same move. Castling can be done on either side of the board. Castling can either be done on the king-side (also known as castling short) or on the queen-side (also known as castling long).