While the chain gang is very competent, officials want to avoid bringing the chains in for a measurement whenever possible. They want to keep the game moving and sometimes measurements cause controversy.
In the NFL, all fields, both grass and turf, are well marked and have a hash stripe for each yard line. Officiating crews at every level start a series of downs on a yard marker, even though there may be a margin of several inches.
Why? Simple. If a new series starts on the 36-yard line on a well-marked field, officials know the 46 is a first down. If a team makes 46 ½, the officials award the first down, and start the next series on the 47-yard line. Teams do not protest this. Starting a first down on a yard marker gives the offense a clear yard line to reach. To tell you the truth, most teams don’t even notice this.
This can leave disbelieving spectators wondering why a close spot isn’t measured, but if the ball is clearly touching the paint of the yard line, this is an easy confirmation.
There is one big exception to this philosophy. If a team goes for it on fourth down and gets stopped at the 45 ½-yard line, the ball goes over on downs and the next series begins at the 45 ½, because officials don’t adjust the (most likely) controversial spot after a turnover on downs. When possession or the game is on the line, the officials will call for the chains, but they try to avoid measurements if possible.
Artificial turf fields never change markings. Grass fields need to be re-striped for every game. The officials make sure the field is properly and accurately marked during their pregame inspection.
The officials do their best to make sure the chains stay on the sideline and thanks to well-marked fields, the chain gang gets less TV time.
Image: San Francisco 49ers photo