While the general characteristics of the game are the same wherever it is played, the exact rules depend on the particular code of play being used. The most important code is that of the Comité International Roller In-Line Hockey (CIRILH), an organization and discipline of the Fédération Internationale de Roller Sports (FIRS) Inline hockey is played on an inline hockey rink. During normal play, there are five players per side on the floor at any time, one of them being the goaltender, each of whom is on inline hockey skates. The objective of the game is to score goals by shooting a hard plastic disc, the puck, into the opponent's goal net, which is placed at the opposite end of the rink. The players may control the puck using a long stick with a blade that is commonly curved at one end. Players may also redirect the puck with any part of their bodies, subject to certain restrictions. Players may not hold the puck in their hand and are prohibited from using their hands to pass the puck to their teammates, unless they are in the defensive zone. Players are also prohibited from kicking the puck into the opponent's goal, though unintentional redirections off the skate are permitted. Players may not intentionally bat the puck into the net with their hands. The four players other than the goaltender are typically divided into two forwards and two defencemen. The forward positions consist of a center and a winger. The defencemen usually stay together as a pair generally divided between left and right. A substitution of an entire unit at once is called a line change. Teams typically employ alternate sets of forward lines and defensive pairings when shorthanded or on a power play. Substitutions are permitted at any time during the course of the game, although during a stoppage of play the home team is permitted the final change. When players are substituted during play, it is called changing on the fly. The boards surrounding the floor help keep the puck in play and they can also be used as tools to play the puck. Players are not permitted to "bodycheck" opponents into the boards as a means of stopping progress. The referees and the outsides of the goal are "in play" and do not cause a stoppage of the game when the puck or players are influenced (by either bouncing or colliding) into them. Play can be stopped if the goal is knocked out of position. Play often proceeds for minutes without interruption. When play is stopped, it is restarted with a faceoff. Two players "face" each other and an official drops the puck to the floor, where the two players attempt to gain control of the puck. Markings on the floor indicate the locations for the "faceoff" and guide the positioning of players. There is one major rule of play in inline hockey that limit the movement of the puck: the puck going out of play. The puck goes "out of play" whenever it goes past the perimeter of the rink (onto the player benches, over the "glass," or onto the protective netting above the glass) and a stoppage of play is called by the officials using whistles. It also does not matter if the puck comes back onto the playing surface from those areas as the puck is considered dead once it leaves the perimeter of the rink. Under FIRS rules, each team may carry a maximum of 14 players and two goaltenders on their roster. The players are usually divided into three lines of two forwards, two pairs of defenceman, and two extra skaters.