A Window Installer Sub Contractor is a skilled professional who installs, replaces, and repairs windows in residential or commercial buildings on a contract basis. They typically work independently or as part of a team, following blueprints and manufacturer specifications to ensure proper fit and weatherproofing. Their responsibilities may include measuring openings, removing old windows, installing new frames and glass, applying sealants, and finishing trim work. Sub contractors are usually hired by general contractors, window companies, or directly by homeowners, and are responsible for providing their own tools, transportation, and sometimes insurance.