Chain crew

In gridiron football, the chain crew (commonly known as the "chain gang") is a crew that manages signal poles on one of the sidelines.

The chain crew, under the direction of the head linesman, signals the officials' decisions; it does not make decisions. Players look to the chain crew to see the down number and the line to gain. Officials may rely on the chain crew after a play (incomplete pass or penalty) whose outcome depends on the original spot of the ball.

Three members of the chain crew hold poles upright. The bottom of each pole is placed along a sideline to denote a line straight across the gridiron to the opposite sideline.

Members of the chain crew are usually picked by the offices of the home team instead of the league or conference. In the NFL, members of the chain crew must have credentials entitling them to access to the field, and must wear white shirts.

The chain crew does not wear protective gear as players do. A routine instruction by officials to the chain crew is to withdraw or drop their signals, and move back, if the play comes toward them so as to endanger them. The signals often use bright orange color and are padded to minimize injury.

For games at all levels below the NFL, the chain crew operates on the side of the field opposite the press box and home team (the side of the visiting team). In the NFL, the chain crew switches sides at halftime; the referee determines their initial placement. On fields where both teams' benches are located on the same side of the field, the chain crew operates on the opposite side for the entire game.

In the NFL and other venues where there is a zone behind the sidelines, all three poles are placed somewhere along the back line of this zone. Otherwise, the poles are placed along the sideline.

For professional and college football games, an auxiliary chain crew operates on the opposite side of the field, supervised by the line judge. Their function is to let players and officials look to either side of the field for information. The auxiliary chain crew also includes the drive start indicator, which is placed at the beginning of a team's drive and stays there until the team loses possession. This indicator is only used for statistical purposes to calculate the distance of each drive. It looks similar to a "stick" and has an arrow (or occasionally a large "X") that points in the direction the offensive team is going.

At the start of a series of downs, the linesman stands so that the heel of one foot marks the initial line of scrimmage. The box man places his indicator to mark this position and sets the box to display "1". The operator of the rear rod marks the same position, while the other rod man moves ten yards toward the defense's goal line to mark the line to gain.

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