How to be a linesperson

1) Ball Out of Play

You have to let the ref know if the ball goes out and who put it out.

• As soon as the whole of the ball crosses the whole of the line put your flag straight up.

• Then point your flag (up at 45°)  in the direction of the team to take the throw-in.

• An easier way to think about it may be to point to the defending end of the team who put it out.

• Keep holding the flag up until either the ref indicates to put it down, or the ref points in the opposite direction, or it’s been long enough for everyone to have seen the decision.

• If the ball goes out over the goal line, put your flag straight up so the ref knows it’s out. Then point your flag directly at the goal-kick area or the corner spot depending on which team touched it last.

2) Offside

You have to let the ref know whenever someone is offside.

To do this you need to stay level with the last defender (not including the goalkeeper) in order to see if anyone is offside.  This usually means walking or crab-stepping sideways so you are always facing the pitch with your flag pointing down where the ref can see it.  Occasionally, you will need to sprint to stay with the last defender.    

          Tip: When running fast, you still need to keep the flag down and visible to the ref.

• To flag offside stop moving and stand still with your flag straight up. Stay like that until you have either been acknowledged by the ref, or it is clear he has chosen to ignore you.   If the ref awards the free-kick for offside, point to where the offence occurred, as shown here. Stay still like that for 10 seconds so everyone can see what the decision was.

 The offside rule (simplified):

Where are they? 

A player is offside if they are nearer to the opponent’s goal than both the ball and the last opponent (excluding the goalkeeper), when their teammate plays the ball to them.

In other words, a player can’t receive the ball from a teammate unless there is at least one defender between him and the goal (unless their teammate is playing the ball backwards).

What are they doing?  

A player is only offside if he/she is 

interfering with play (Eg. part of the attacking move)

or interfering with an opponent (Eg. preventing the opponent from defending against the attacking move)

or gaining any advantage by being in that position.

Exceptions.  

A player can’t be offside

• in their own half

• from a goal-kick

• from a throw-in 

• from a corner

For more details see the FIFA Offside PDF.

3) Other Linesperson Duties

Substitutions

As soon as the ref gives permission for a sub to occur, hold your flag horizontal over your head with your arms straight until the ref signals for play to resume. 

Unseen Incidents

Keeping one eye on 22 players is an impossible task for the referee. The linesperson, therefore, acts as a second pair of eyes. It is their duty to indicate when an incident occurs out of the referee’s view by holding the flag straight up.

Better View

If the referee believes the linesperson had a better view of an incident, they will consult with the linesperson to determine the correct course of action.

The linesperson must look along the goal line and decide whether the goalkeeper moved off the goal line before the penalty-taker kicked the ball. They decide whether the ball crossed the goal line.

Entering the Field of Play

Linesmen rarely enter the field of play, remaining on the sideline for most of the game. If needed, a linesperson can enter the field of play to assist the referee during free-kick procedures, specifically to help enforce the 10 yards law. Linesmen also help the referee when scuffles or fights occur. According to the FIFA Laws of the Game, the nearest assistant referee may enter the field of play to assist the referee in situations of mass confrontation.

When you aren’t using the flag, keep it down and on pitch-side of your body so the ref can see it at all times. Especially don’t wave it about unless you want the refs attention.

Source: Gameday