The general rule for any tool that touches a client's skin, nails, or hair is:

The general rule across all cosmetology services is that any tool contacting a client's skin, nails, or hair must be cleaned and disinfected (if nonporous and reusable) or discarded (if single-use/porous) before it is used again. This single principle underlies infection control for hair, skin, and nail services alike. The exam repeatedly tests whether candidates apply this rule consistently to every implement and service. Internalizing it as a universal habit is one of the most important safety takeaways of the licensing exam.