A Rook is of the value of five Pawns and a fraction, and may be exchanged for a minor Piece and two Pawns. Two Rooks may be exchanged for three minor Pieces.
The Bishop and Knight, in contradistinction to the Queen and Rook, are called Minor Pieces.
A Pawn reaching the eighth square must be at once exchanged for any piece of its own color (except the King) that the player of the Pawn may elect.
The action of the Knight is peculiar, and not easy to describe. He is the only one of the Pieces which has the privilege of leaping over another man.
When the King is checked, or any valuable Piece in danger from the attack of an enemy, you are said to interpose a man when you play it between the attacked and attacking Piece.