Disadvantages abound in any blitz scheme as well. First, the offensive linemen are usually trained to recognize a blitzing player before the snap of the ball. They communicate with each other at the line of scrimmage using code words that shift the protection to the blitzing player's side, thus strengthening their blocking front. The quarterback can also call other players into the protection scheme with audibles if he feels that his current protection is weak. With good protection calls and fundamental blocking principles, some blitzes can be "picked up" — stopped at the point of attack.