What is a window sash?

A window sash is the part of a window that holds the glass panes in place and allows them to open and close. It is typically made of wood, metal, or vinyl and is fitted with hinges and locks so that it can be opened or closed for ventilation or cleaning. The sash is usually divided into sections, known as lights, that are filled with glass panes. Double-hung windows have two sashes that slide up and down, while casement windows have one or more sashes that swing outward on hinges. The sash is an important component of a window, as it helps to provide insulation, security, and protection from the elements.