a mix of the two sports' rules. Comparison with gridiron codes Much more so than rugby union, rugby league shares significant similarities with North American gridiron codes. Although described as evolving from both rugby and association football, the basic structures of American and Canadian football are remarkably similar to rugby league through a process of parallel evolution: a try-and-goal based scoring system, a set number of plays before handover of the football, each play restarting from a set piece position and ended by a tackle. The introduction of the forward pass and unlimited substitution in North America, however, created a fundamentally different game from either original rugby code. Positions Players on the pitch are divided into forwards and backs, although the game's rules apply to all players the same way. Each position has a designated number to identify himself from other players. These numbers help to identify which position a person is playing. The system of numbering players is different depending on which country the match is played in. In Australia and New Zealand, each player is usually given a number corresponding to their playing position on the field. However, since 1996 European teams have been able to grant players specific squad numbers, which they keep without regard to the position they play, similarly to association football. Substitutes (generally referred to as "the bench") are allowed in the sport, and are typically used when a player gets tired or injured, although they can also be used tactically. Each team is currently allowed four substitutes, and in Australia and New Zealand, these players occupy shirt numbers 14 to 22. There are no limitations on which players must occupy these interchangeable slots. Generally, twelve interchanges are allowed in any game from each team, although in the National Rugby League, this was reduced to ten prior to the 2008 season and further reduced to eight prior to the 2016 season. If a team has to interchange a player due to the blood bin rule or due to injury, and this was the result of misconduct from the opposing team, the compromised team does not have to use one of its allocated interchanges to take the player in question off the field. Backs The backs are generally smaller, faster and more agile than the forwards. They are often the most creative and evasive players on the field, relying on running, kicking and handling skills,