Make sure your students know when to refer a client to a doctor. This handout, made especially with nail students and newbie nail techs in mind, describes 23 of the most common nail disorders -- like brittle nail syndrome and "greenies" -- and tells nail techs when to refuse service and refer a client to a doctor first. This chart was reviewed by Dr. Johanna Youner, an attending podiatric physician and surgeon at New York Downtown Hospital. (When in doubt, don't service a client without a doctor's note.)