Before a game can begin, every stick that each player is planning on using the game must be approved by the referee based on a set of standards created by the U.S. Lacrosse and NCAA. These standards are constantly changing as new sticks are being created by different lacrosse companies. Often a standard lacrosse ball is placed into the head of the stick and viewed by the referee at his/her eye level. If the ball cannot be seen over the top of either side of the head, then the pocket is most likely too deep for play. A pocket that is deeper than regulation causes an unfair advantage to that individual with the stick. If the stick pocket is too deep, this can often be fixed by tightening the stringing. If a stick is strung incorrectly by the manufacturer, the stick cannot be used in the game. An example of stick stringing regulation is that the shooting string attachment must be 3.5 inches from the top of the head. After someone scores a goal, the referee has the right to ask to check her stick. If the stick's pocket is to deep or the stick does not follow the standards now for some reason, the goal will be called back. Also, on a winning shot the other team is allowed to challenge the player's stick.