Only the flat side of the curved, hardwood stick can be used to touch the ball. The obstruction rule is unique to field hockey. Shielding the ball with one's body is an important aspect of game strategy in almost every other sport. However, in field hockey, this is not permitted. Instead, players must keep their hands on or near their hips. The only way a player can touch the ball with his or her hand or arm is if it is wrapped up completely in a shirt or jacket. Then that part of the body can act as a shield for the ball. However, even then, the hand or arm cannot be extended beyond the shoulder. If it is, then the handler will be penalized for holding back on the attack. Field hockey uses a flat ball that is approximately 12 inches in diameter. It is composed of leather and rubber strips, which are glued together. The ball is heavy for its size, which makes it difficult to handle. It can be kicked, but not batted like a cricket ball. During a field hockey game, each team will have a number of players positioned in the "attack zone" who try to score by kicking or hitting the ball into the opposing goal. These players often travel in straight lines across the field or use short passes to move the puck around the field.