Documented vessels do not display their official numbers on the outside of the hull, but are identified by the name and hailing port. The application for documentation must include a name for the vessel composed of letters of the Latin alphabet or Arabic or Roman numerals and may not exceed 33 characters. The name may not be identical, actually or phonetically, to any word or words used to solicit assistance at sea; may not contain or be phonetically identical to obscene, indecent, or profane language, or to racial or ethnic epithets. Once established, a vessel’s name may not be changed without application, fees, and the consent of the Director, National Vessel Documentation Center. There is no rule against duplication of names for documented vessels, so hailing ports are helpful in identifying vessels.