The purpose of the build-out line is to encourage players to build-out from the back using the goalkeeper as not just a shot stopper but a field player as well.    By restricting the length of passes, players that play in the back will be put into a situation where they have to make decisions on the ball as opposed to only defending.  

Build-out lines are used for U7-U10 soccer.  The rules are very simple but will take some getting used to.  Here's a short video to understand the rules.



Below are diagrams to help understand the rules of the build out lines.

1.) When the goalkeeper has possession of the ball, the opposing team must retreat behind the build out line.  The goalkeeper's teammates are allowed to be within their build out line.

2.) The goalkeeper does not have to wait on the opponents to retreat behind the build out line and is allowed to pass the ball immediately.  If the goalkeeper chooses to do so, no infraction will be called against the opposing team for being past the build out line.

3.) The goalkeeper is not allowed to punt or drop-kick the ball.

1.) Offside can only be called beyond the opponents build out line.
2.) A player is offside if the player is standing beyond the opposing build out line the moment the ball is passed.

     

1.) No pass can cross both build out lines without touching the ground in the central section between both build out lines.  Even if the receiving player is onside.
2.) Goalkeepers are not allowed to punt or drop-kick the ball.