Careers in plumbing normally require the completion of an apprenticeship, although some have gained experience as assistants. Others attend a technical school to earn a degree, the credits for which can be applied toward completing an apprenticeship. Technical schools offer courses on pipe system design, safety, and tool use, as well as welding courses considered to be necessary by some pipefitter and steamfitter apprenticeship training programs. Although there are many routes to becoming a plumber, a high school diploma or the equivalent is required, as is licensing in many states in the US.