A barbershop may not employ at the same time more than three apprentice barbers for each master barber employed. A barbershop may have a separate shampoo area. The Board may not require a barbershop to have a minimum number of sinks. An apprentice barber under complete and constant supervision of a master barber may assist the master barber in starting or completing an operation. The master barber or barbershop may charge the usual fees for the operation. A fee may not be charged for an operation performed completely by an apprentice barber.