Md. Code, Business Occupations and Professions § 12–604

Unless authorized under this title to provide plumbing services, a person may not represent to the public, by use of a title, including “master plumber”, “registered plumber”, “licensed master plumber”, “holder of limited master plumber license”, “licensed journey plumber”, “journey plumber”, “holder of a limited journey plumber license”, “holder of a propane gas fitter certificate”, “holder of a master natural gas fitters license”, “holder of a journeyman natural gas fitters license”, or “holder of an apprentice natural gas fitters license”, by description of services, methods, or procedures, or otherwise, that the person is authorized to provide plumbing services in the State.