There are roughly 24 different hand signals used by volleyball referees, including point, substitution, line violation and illegal hit. To signal a point, referees place their hands straight out from their bodies to the left. To indicate a substitution, arms go in front of the chest in a circular motion.
For a referee to indicate a line violation, the left hand needs to be slightly extended, and it needs to point downward. The illegal hit signal is shown by raising the right hand up in a slower motion. Other hand signals in volleyball include illegal alignment or improper serve, delay of service, over the net, net foul or serve, legal back row attack, illegal block, illegal attack of serve, "ball touched," four hits, double hits, ball landing inbounds, out of bounds violation, begin serve, authorization to enter, point, re-serve, illegal substitution, team time out, official time out, unnecessary delay and change of courts.
To make a delay of service signal, referees hold one palm up in the air at a 90-degree angle. An illegal block signal requires both hands to be raised in the same manner. A double hit call is similar to delay of service, but two fingers are held up as opposed to a palm.