During volleyball matches you can often see a huge rotation of players. The player who enters take a paddle and gives it to the player who comes out. What is the significance of the paddle?
The number on the paddle is the number of the player who is being substituted. This is important due to the volleyball rules on reverse substitutions: if in a set, player B replaces player A, then the only substitution which can be made involving players A and B for the rest of the set is for player A to replace player B again. For example, you cannot do the following substitutions within one set:
- Player B replaces player A
- Player C replaces player B
This is covered by rule 15.6:
15.6 LIMITATION OF SUBSTITUTIONS
A player of the starting line-up may leave the game, but only once in a set, and re-enter, but only once in a set, and only to his/her previous position in the line-up.
A substitute player may enter the game in place of a player of the starting line-up, but only once per set, and he/she can only be substituted by the same starting player.
Adding to @PhilipKendall's great answer, the paddle in volleyball basically has the same functions as the electronic substitution board used in football. But the main difference is the paddle is carried by a player to hand over to the substituted player while the board is used by the fourth official.
They are used for the same purpose, i.e., to easily notify the substituted player, referees, and other officials that include those who monitor rule violations.
The main reason the paddle is used is to help keep track of the substitutions more easily for everybody involved. As multiple substitutions are allowed in volleyball, unlike football, including that for a libero who can be substituted as many times as possible, monitoring the number of substitutes and who is substituted is extremely difficult not only for officials, but also for coaches and players. Also, there is one more exception that an injured player (except the libero) could be substituted by another player beyond the limits of Rule 15.6.
What is the significance of the paddle?
It makes lives of everybody involved in the game easier.