Window operation is one of the most crucial choices to consider when selecting a window sash. Offering a variety of styles and functions applicable to specific conditions, a range of window operations should be considered to best meet your needs for ventilation, operability, screening, and daylighting. The primary difference between window operation types are between projected or hinged types such as casement, awning, and hopper windows and the sliding variety of windows that includes double-hung, single-hung, and sliding types. Other specialty types include pivoting, jalousie, skylights, and storm windows.