Window fitters measure, supply and install windows in homes and commercial buildings. They work with a range of frame materials, including uPVC, timber, aluminium and composite, and fit different styles such as casement, sash, tilt-and-turn and fixed windows. Work may involve removing existing frames, preparing openings, securing new units, fitting glazing and seals, and finishing the surrounding interior or exterior surfaces. Some businesses also repair or adjust windows, replace broken or misted double-glazed units, renew hinges, handles and locks, and address draughts or water ingress. Customers may ask for advice on glazing options, ventilation, security, thermal performance and matching the appearance of existing windows. Where replacement work is covered by building regulations, the installer or homeowner must ensure the relevant requirements are met; registered competent-person schemes can allow eligible installers to self-certify certain work.