1) Ball Out of Play

If the ball goes out over your touchline, then

1. Stop running
2. Get the flag into your correct hand (no crossovers)
3. Hold it up at 45° in the direction of the team to take the throw.
4. If the ref is pointing the other way, then change your direction to agree with the ref.   
5. Keep indicating for a minimum of 3 secs.  Longer if can see the wrong team is lining up to take the throw.
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If the ball goes out over your goal line, then

1. Stop running
2. Get the flag into your right hand (no crossovers)
3. For a goal kick, point it straight at the goal box.
4. For a corner, point your flag downwards towards the corner nearest to you. Regardless of which side the corner is to be taken from.
5. If the ref is pointing the other way, then change your indication to agree with the ref.  
6. Keep indicating for a minimum of 3 secs.  Longer if can see the teams are lining up against the decision.
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2) Offside

Standing in an offside position when the ball comes forward doesn’t mean they are offside. Don’t flag for offside unless they actually get the ball or they tackle a defender.

Other situations also count as ‘interfering with play’, eg, drawing a defender but these are a bit obscure for this basic page.

You need to run to stay level with the last defender in order to see if anyone is offside. Unless signalling, always keep your flag pointing down and pitchside so the ref can see it even when you are sprinting.

To indicate offside:

1. Stop moving.
2. Stand still with your flag straight up.
3. Stay like that until a) the ref blows the free-kick, b) the refs waves you down, c) More than 15 seconds have passed and the game has moved 3-4 plays ahead of the offence.
4. Once the ref blows the free-kick for offside, then lower your flag to point to where the offence occurred as shown here.
5. Stay still like that until the ball has been placed for the free-kick. You are telling the ref and the players where to take the kick from.

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
  • directly from a goal-kick
  • directly from a throw-in
  • directly from a corner kick

Try a Video Offside Test here 

3) Other Linesman Duties

• Substitutions
  As soon as the ref gives permission for a sub to occur, hold your flag horizontally over your head with your arms straight until the ref signals for play to resume.
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• Unseen Incidents
  Keeping one eye on 22 players is an impossible task for the referee. The linesman, therefore, acts as a second pair of eyes. It is his 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 linesman had a better view of an incident, she will consult with the linesman to determine the correct course of action.
  .

• Penalty Kicks
  The linesman must stand on the goal line where the side of the penalty box meets it and

   

  1. decide whether the goalkeeper moved off the goal line before the penalty-taker kicked the ball.
  2. 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 linesman 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..

• 

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