Definition: Assistants to the officials whose job is to mark where a team begins a series and how far they need to go to get a first down.
Examples:
The chain gang brings the chains onto the field for measurements on plays that end too close to the first down for the officials to make a determination by simply comparing the spot of the ball with the marker on the sideline. The chains are brought out to give an exact measurement from the spot where the series started.
