In basketball, you can block a player as long as your feet remain immobile and your hands are kept to yourself. Any other type of blocking is regarded as a foul. Illegal guarding is the purposeful use of your body to delay or restrict the movement of an opponent player. This includes holding up arms, legs, and hips. There are three types of illegal defenses: screening, hooking, and batting. In each case, the defender uses his or her body to impede an opponent's path to the basket. Screens are used to open up driving lanes for teammates by removing defenders from the play. A screener cannot touch the ball until it has been passed to him or her by a teammate. Hooks are defensive maneuvers where the defender sticks his arm into the path of the on-ball player. This prevents the on-ball player from getting past him or her. Bats are used to defend against players who want to take themselves out of the game. If a player bats himself or herself out of contention, that player becomes ineligible to reenter the game. A legal shot is one taken with proper form. An illegal shot is any shot not taken with proper form, including shots blocked with excessive force. Excessive force means using more than necessary force to block a shot. For example, if a defender uses only his or her forearm to block a shot, then it was not done with sufficient force.