http://www.castlesandmanorhouses.com/chessrook.htm
In chess the castle is a major piece, now usually called a rook. Each player starts with two rooks, one in each of the corners nearest his own side. Like other pieces, the castle captures by occupying the square on which an enemy piece stands. The castle also participates, along with the king, in a special move called castling.
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http://www.learnchessrules.com/castling.htm
Castling is a special defensive maneuver. It is the only time in the game when more than one piece may be moved during a turn.
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Strategy Note: Castling is a great aid in defensive strategy. It also has a tendency to bring a powerful rook into play when under normal circumstances it might be stuck behind a wall of pawns.
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https://www.chess.com/forum/view/general/13-checkmates-you-must-know
Anastasia’s checkmate
This checkmate is another great example of how the knight can be used in mating schemes. In Anastasia’s mate knight and rook work together to lock an opponent’s King on the h – file (it works as well on a - file too, in case of a long side castle) and to checkmate thereafter.
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http://www.dailymail.co.uk/sciencetech/article-3430794/Facebook-secret-chess-game-hidden-messenger-FBChess-accessed-specific-command.html