LAW 3: NUMBER OF PLAYERS - THE TEAM

3.5 (c) If a team nominates 22 players, it must have at least six players who can play in the front row in order that there is replacement cover for the loose head prop, hooker and tight head prop.
If a team nominates more than 22 players it must have at least six players who can play in the front row in order that there is replacement cover for the loose head prop, hooker and tight head prop. There must also be three players who can play in lock position.

3.12 A player who has been substituted may replace an injured player.