These occupations include trades supervisors and contractors, construction and mechanical tradespersons, operators of transportation and heavy equipment and trades helpers. These occupations are found in a wide range of industrial sectors, with many in the construction and transportation industries. This category includes most of the apprenticeable trades, including all those related to the construction industry. Other occupations in this category usually require completion of college or vocational education programs combined with on-the-job training. Helpers obtain training on the job site. Progression to supervisory positions or self-employed contractor status is possible with experience. There is limited mobility or transferability of skills among occupations in this category due to specific apprenticeship, training and licensing requirements for most occupations.