Dhobi - Washermen
Dhobi are part of the Shudra. Within the caste of Shudra there are many different groups.  Each one of these groups performs a service.  Their specific service is a birthright and is somewhat similar to unions in the U.S.  They wash the clothing for all the different caste levels.  Without the Dhobi, everyone would walk around with dirty stinky cloths.