The field and equipment

The field. Football is played on a level area 120 yards (110 meters) long and 531/2 yards (49 meters) wide. The field may have a surface of natural grass or of a synthetic material. All indoor stadiums use green synthetic surfaces that look like grass. Many outdoor stadiums also use synthetic surfaces.

The football field is marked with white lines. It is often called a gridiron because the pattern of lines resembles the cooking utensil used to broil foods. A sideline borders each of the two long sides of the field. Any player who touches or crosses a sideline is ruled out of bounds. Yard lines cross the field every 5 yards (4.6 meters). Near each end of the field is a goal line. The goal lines are 100 yards (91 meters) apart. An area called an end zone extends 10 yards (9 meters) beyond each goal line. The yard lines are numbered from each goal line to the 50-yard line, or midfield.

Two rows of lines, called hash marks, parallel the sidelines. All plays start with the ball between or on the hash marks. If a play ends out of bounds or between the hash marks and the sideline, the ball is placed on the nearest hash mark for the next play.

In high school and college football, two goal posts stand on the end line 10 yards behind each goal line. A crossbar connects the posts 10 feet (3 meters) above the ground. In the NFL, a single post 6 feet (1.8 meters) behind the end line curves forward and supports the crossbar directly over the end line. In high school games, the goal posts are each 20 feet (6 meters) high and 23 feet 4 inches (7 meters) apart. In college and NFL football games, the goal posts are each 30 feet (9 me-ters) high and 18 feet 6 inches (5.6 meters) apart.

The ball is oval. It is about 11 inches (28 centimeters) long and about 7 inches (18 centimeters) in diameter at the center. Balls used in high school, college, and professional games are made of four pieces of leather stitched together. Footballs used in recreation may be made of rubber or plastic. A football has a rubber lining, which is inflated to an air pressure of 121/2 to 131/2 pounds per square inch (0.88 to 0.95 kilogram per square centimeter). The ball weighs 14 to 15 ounces (397 to 425 grams). Leather laces along one seam provide a grip for holding and passing the ball.

The uniform. A football player's uniform is made of cotton or nylon and consists of a shirt and pants. The shirt, which is called a jersey, has the player's number--and sometimes his name--sewn on the back and front for identification by the officials and spectators. In most cases, the players wear jerseys and pants of different colors. The uniforms fit tightly so that opposing players cannot easily grasp them when trying to block or tackle.

Protective equipment helps prevent injuries. The amount of equipment a player wears depends on his position. The section called The players and coaches describes the duties of the various players. Linemen wear more protective equipment than other players because they are involved in the most physical contact through blocking and tackling. Backs and ends wear less equipment so that they can run at top speed.

Each player wears a helmet held in place with a chin guard. The helmet has a face mask. Most players also wear a mouthpiece to help prevent injuries to their teeth. Under their uniforms, the players wear shoulder pads, hip pads, thigh pads, and knee pads. In many cases, the thigh pads and knee pads are sewn into the pants. Some players also use arm guards, elbow pads, rib pads, and liners to protect the shins.

Football players wear shoes that help prevent slipping and provide good traction for running. When the game is played on grass, players wear shoes with cleats. On synthetic surfaces, they wear shoes with specially designed soles for better traction. Some players wear high-top shoes that lace up to their ankles. The lacing gives the ankles more support and helps prevent sprains. Most backs and ends prefer low-cut shoes that enable them to make quick cuts (changes in direction) during the game.