<P> The defensive backfield, often called the secondary, consists of cornerbacks (CB) and safeties (S). Safeties are themselves divided into free safeties (FS) and strong safeties (SS). Cornerbacks line up outside the defensive formation, typically opposite of a receiver so as to be able to cover him, while safeties line up between the cornerbacks but farther back in the secondary . Safeties are the last line of defense, and are responsible for stopping deep passing plays as well as running plays . </P> <P> The special teams unit is responsible for all kicking plays . The special teams unit of the team in control of the ball will try and execute field goal (FG) attempts, punts and kickoffs, while the opposing team's unit will aim to block or return them . </P> <P> Three positions are specific to the field goal and PAT (point - after - touchdown) unit: the placekicker (K or PK), holder (H) and long snapper (LS). The long snapper's job is to snap the football to the holder, who will catch and position it for the placekicker . There is not usually a holder on kickoffs, because the ball is kicked off of a tee; however, a holder may be used in certain situations, such as if wind is preventing the ball from remaining upright on the tee . The player on the receiving team who catches the ball is known as the kickoff returner (KR). </P> <P> The positions specific to punt plays are the punter (P), long snapper, and gunner . The long snapper snaps the football directly to the punter, who then drops and kicks it before it hits the ground . Gunners line up split outside of the line and race down the field, aiming to tackle the punt returner (PR)--the player that catches the punt . </P>

How many players on a youth football team