A device used to denote the ten yards from the point where a first down was awarded to the yard line an offense needs to reach to receive a new set of downs. The chain is a ten yard metal chain with two tall orange indicators on either end of the chain. The orange indicator is an inverted skinny orange triangle with a bullseye style circle on the top. The chains are also used to verify first downs in the event that the referee wants to measure the spot of the ball.
The chains are the main way players on the field will determine where the first down marker is. For offensive players, the chains are valuable because it gives them a visual cue when running towards the sideline of where they need to get to for a first down. After each first down, the chains on either side are quickly relocated to the new line of scrimmage. During a measurement, the chains from one side of the field will be brought out and stretched to determine whether or not a team has received a first down.