Assistant referees were known as linesmen until 1996. They assist the referee in controlling a football match from the touchlines and are concerned mainly with indicating when the ball is out of play, offside, throw-in decisions and committed offences outside the referee’s view. The assistant referees also help the referee in decisions that needs further clarification.
During a football match, one assistant referee oversees one touchline and one end of the pitch while the other is responsible for the other touchline and the other end of the pitch.
There are two assistant referees during a football match and a fourth official, who assists with administrative tasks such as; substitutions, player equiupment checks, and contact with team officials. The fourth official will also act as replacement for a referee in case of injury.
For the 2006 FIFA World Cup a fifth official was introduced. This person assists the fourth official and will act as replacement in case of injury.