fullback. Overview There is a maximum of 15 players from each team allowed on a rugby field at any one time. The players' positions at the start of the game are indicated by the numbers on the backs of their shirts, 1 to 15. The positions are divided into two main categories; forwards (numbered 1 to 8) and backs (numbered 9 to 15). In international matches, there are eight substitutes that can replace an on-field team-mate. The substitutes, numbered 16 to 23, can either take up the position of the player they replace or the on-field players can be shuffled to make room for this player in another position. Typically, the forwards among the substitutes will have lower numbers than the backs. There are no personal squad numbers and a versatile player's position and number may change from one game to the next. Players can also change positions during the match; common examples are the fly-half playing the full-back's position in defence or a prop taking the hooker's position at line-outs. Different positions on the field suit certain skill sets and body types, generally leading to players specialising in a limited number of positions. Each position has certain roles to play on the field, although most have been established through convention rather than law. During general play, as long as they are not offside, the players may be positioned anywhere on the field. It is during the set pieces (scrum and line-out) that the positions are enforced. History During early rugby union games there were only really two positions; most players were in the forwards, who formed part of the scrimmage (which later was called "scrummage" and then "scrum"), and a few defensive "tends" (from "goaltenders"). Eventually, the attacking possibilities of playing close behind the scrimmage were recognised. The players who stationed themselves between the forwards and tends became known as "half-tends". Later, it was observed that the players outside scrimmage were not limited to a defensive role, so the tends and half-tends were renamed "backs" and "half-backs". As the game became more sophisticated, the backs positioned at different depths behind the forwards. They were further differentiated into half-backs, three-quarter-backs, and full-back. Specialised roles for the scrum also evolved with "wing-forward" (modern day flankers) being employed to protect the half-back. The first international between England and Scotland was played in 1871 and consisted of 20 players on each side: thirteen