NFL hash marks are 18 feet apart. College is 40.

Ask what separates college football from the NFL and you will hear about talent, speed and scheme. The most consequential difference is a pair of painted lines.

The numbers

NFL hash marks are 18 feet 6 inches apart. College hash marks are 40 feet apart — more than double.

Why it changes the sport

In college, most snaps start near a hash, which means one side of the field is enormous and the other is cramped. Defenses have to shade toward the wide side. That tips their hand: a quarterback and his linemen can read the alignment before the snap, and it becomes hard to disguise a blitz or a coverage when there is simply too much grass to cover.

In the NFL, the ball is always near the middle. So the defense can lie.

Narrow hashes keep the ball near the centre of the field. A defense can line up balanced, which means the same look can become several different coverages. Disguise becomes possible, and aggression becomes affordable.

The transition problem

This is one reason college production does not always survive the jump. A quarterback whose pre-snap reads were partly handed to him by the field's geometry arrives in a league where the geometry stops helping, and defenses stop announcing themselves.