The rook moves any number of empty squares horizontally or vertically, along ranks and files. It cannot move diagonally and cannot jump over other pieces. Rooks are strongest on open files, which are columns with no pawns, and on the opponent's back ranks. They also take part in castling, the special king-and-rook move. Try to connect your rooks by clearing the pieces between them, and double them on an open file to increase pressure. Rooks are usually developed later than knights and bishops, once the centre is settled and lines have opened.