A marker on the field that marks in yards the distance to the closest goal line.
The football field is 120 yards long and 160 feet wide with 100 yards being the playing field. The end zones are 10 yards thus making up the remaining 20 yards of the field. The yard lines cross the field and are spaced 5 yards apart. The middle of the field is marked by the 50 yard line with the rest of the yard lines being marked every 10 yards to the goal line. From one side the yard lines will increase up to the 50 yard line then begin to decrease down to the other goal line. Example: 10, 20, 30, 40, 50, 40, 30, 20, 10. These markers help to determine how many yards a team has gained. A team must gain 10 yards for a successful first down. The yard lines help to determine whether the team has been successful or not.