- Replacements involving the libero are unlimited and are not counted as regular substitutions.
- There must be a completed rally between two libero replacements (unless a penalty forces a rotation into position 4, or the acting libero becomes unable to play).
- The libero may be replaced only by the player they replaced, or by the second libero.
- Replacements happen while the ball is out of play, before the whistle for service, through the libero replacement zone.
- At the start of each set the libero may enter only after the second referee has checked the line-up.
- Pass serve
- Dig
- Set from behind the attack line
- Replace any back-row player (unlimited)
- Serve (FIVB)
- Block or attempt to block
- Attack a ball fully above the net
- Be a front-row player