White markings on the field identify the distance from the end zone. Inbound lines, or hash marks, are short parallel lines that mark off 1 yard (0.91 m) increments. Usually, every 5 yards (4.6 m) they run the width of the field. A one yard wide is placed at each end of the field; this line is marked at the center of the two-yard line in professional play and at the three-yard line in college play. Numerals that display the distance from the closest goal line in multiples of ten are placed on both sides of the field every ten yards. Lines marked along the ends and sides of the field are known respectively as the end lines and sidelines, and goal lines.
- NFL Rules 2012, p. v, 1.
- NCAA Rules 2011–2012, pp. 18–19, 23–24.
- NFHS Rules 2012, pp. 11–12, 13, 28.