ball that deflects off the block back into their own court. Popular formations include the 2-3 system and the 1-2-2 system. In lieu of a system, some teams just use a random coverage with the players nearest the hitter. Defensive systems are the formations used by the defence to protect against the ball being grounded into their court by the opposing team. The system will outline which players are responsible for which areas of the court depending on where the opposing team is attacking from. Popular systems include the 6-Up, 6-Back-Deep, and 6-Back-Slide defence. There are also several different blocking schemes teams can employ to disrupt the opposing teams' offence. When one player is ready to serve, some teams will line up their other five players in a screen to obscure the view of the receiving team. This action is only illegal if the server makes use of the screen, so the call is made at the referee's discretion as to the impact the screen made on the receiving team's ability to pass the ball. The most common style of screening involves a W formation designed to take up as much horizontal space as possible. Strategy Player specialization There are five positions filled on every volleyball team at the elite level. Setter, Outside Hitter/Left Side Hitter, Middle Hitter, Opposite Hitter/Right Side Hitter and Libero/Defensive Specialist. Each of these positions plays a specific, key role in winning a volleyball match. Setters have the task for orchestrating the offence of the team. They aim for the second touch and their main responsibility is to place the ball in the air where the attackers can place the ball into the opponents' court for a point. They have to be able to operate with the hitters, manage the tempo of their side of the court and choose the right attackers to set. Setters need to have a swift and skillful appraisal and tactical accuracy and must be quick at moving around the court. At elite level, setters used to usually be the shortest players of a team (before liberos were introduced), not being typically required to perform jump hits, but that would imply need for short-term replacement by taller bench players when critical points required more effective blocks; in the 1990s taller setters (e.g. Fabio Vullo, Peter Blangé) began being deployed, in order to improve blocks. Liberos are defensive players who are responsible for