Club Linesmen (who may be male or female) assist the center referee in a manner similar to assistant referees but with easy and limited responsibilities -- notably just signalling when the ball is out of play by raising a flag or their hand if no flag was provided.
Normally Club Linesmen should only move along their assigned touchline between the halfway line and the goal line. They should move up and down the touchline to stay level with the ball as it travels their half of the field. The Linesmen should always have a clear line of site down the touchline in both directions and across the goal line when the ball is near the goal line.
If a Club Linesman wishes to be stationary, the best location to stand is at the corner flag to the right of the touchline to which the Referee assigned him. This allows the Linesman to see clearly down both his touchline and one goal line. Thus the 2 Linesmen can cover all four boundaries of the field since each has 1 touchline and 1 goal line.
The Club Linesmen should make sure that all items, spectators, coaches, and players who are not playing stay at least 3 feet away from the touchline so they do not hinder play or interfere with the Club Linesman's clear line of sight.
A soccer ball is out of play only after the entire ball crosses the vertical plane formed by the outside edge of the touchline or goal line and extending upward into space and perpendicular to the playing field. Club Linesman should always be immediately next to or on the touchline so they can clearly see down that plane and determine whether the ball has passed completely through the plane whether on the ground or in the air.
Club Linesmen may cheer for either or both teams but must give no on field instructions. It is preferred if Club Linesman can be relatively quiet during the game and just do their duty.
Training: The Referee will briefly train Club Linesman before the game starts so they know when the ball is out of play and where the Club Linesman should be during the match.
Time Commitment: From the time the Referee appoints the Club Linesman until the Club Linesman returns the flag to the referee.
Being a Club Linesman is fun, allows a clear unobstructed view of the game, and gives the person a small taste of what it is like to be an assistant referee. Every parent should give it a try. It's easy and fun!