The residential sector of construction is focused on the construction, modification, and repair of the homes we live in. Although this is the model that we primarily teach to at the Career Center, it is only one of the major avenues in the construction industry. Some workers choose to specialize on one part of the homebuilding process and work as sub-contractors in their trade. A licensed builder or general contractor normally coordinates the project and "subs out" at least part of the work to those people. Many subs such as plumbers, electricians, and heating contractors are required to have specialized licenses that allow them to work in those trades.