Clear and Contain

A clearance sacrifice is a tactical motif which involves a square on the chessboard being vacated to open up lines of attack. The tactic may also result in the substitution of a piece hindering the attack by a piece useful to the attack.

A mating net is when your pieces work together to prevent the opposing king from escaping a mating attack. Not all moves in a mating attack have to be check. Sometimes it helps to play a quiet move to prevent the king from escaping before you checkmate.

In this game, 21. f6 secures a mating net from which the Black King cannot escape.