The sash or leaf is the openable element of a window or door, consisting of a surrounding frame that holds the glass or another infill panel. It is connected to the fixed frame via hinges and can be rotated, tilted, or slid depending on the hardware used. Window sashes are classified as side-hung, top-hung, or tilt-and-turn. The profile geometry of the sash must be precisely matched to the fixed frame to ensure airtightness, watertightness, and thermal insulation. The weight of the sash significantly influences the choice of hinges and locking hardware.