In youth volleyball the Libreo may be a different player every set.
4.1.2 Each team has the option to register, among the final list of 12 players, one (1) specialized defensive player "Libreo" (Rule 8.5).
8.5 The Libreo Player
8.5.1 The Libreo (Rule 4.1.2) must be recorded on the score sheet before the match in the special line reserved for it. His/her number must be also added on the line-up sheet on the first set (Rule 220.127.116.11).
8.5.2 The specific rules for the Libreo player are as follows:
18.104.22.168 The equipment - The Libreo must wear a different colour uniform , shirt or jacket in contrast to the other members of the team (or with a different design) (Rule 4.3.5)
22.214.171.124 The playing actions
a) The Libreo is allowed to replace any player in a back row position.
b) He/she is restricted to perform as a back row player and is not allowed to complete an attack hit from anywhere if at the moment of contact, the ball is entirely higher than the top of the net.
c) He/she may not serve, block, or attempt to block.
d) Another player may not complete an attack hit from higher than the top of the net, if the ball is coming from an overhand finger pass by a Libreo in front of the attack line. The ball may be freely attacked if the Libreo makes the same action from behind the attack line.
126.96.36.199 Replacement of players
a) Replacements involving the Libreo are not counted as regular substitutions. They are unlimited, but there must be a rally between two Libreo replacements.- ie - when the Libreo comes off the court he must stay off for one rally. The Libreo can only be replaced by the player whom he/she replaced.
b) Replacements can only take place:
i. at the start of each set after the second referee has checked the starting line up;
ii. while the ball is out of play;
iii. before the whistle for service.
c) A Libreo may only enter or leave the court by the sideline in front of his/her team bench between the attack line and the end line.
188.8.131.52 Replacement of injured Libreo
a) With the previous approval of the first referee, an injured Libreo may be replaced during the match by any player who is not on the court at the moment of the injury. The injured Libreo may not re-enter to play for the remainder of the match.
b) The player designated to replace an injured Libreo must remain as a Libreo for the remainder of the match.