The duties of a door installer are to install, service, or repair doors for residential or commercial customers. These may install an interior or exterior doors, or automatic doors with mechanical or hydraulic components. Qualifications vary, but on-the-job training is often available. If they commonly work with automatic doors, mechanical aptitude and some knowledge of how hydraulic components work may be important. For standard exterior and interior doors, employers may prefer basic carpentry skills and general knowledge of tools.