- Sash balance: A system of weights, cords and/or coiled springs which assist in raising double-hung sash and tend to keep the sash in any placed position by counterbalancing the weight of the sash.
- Sash lock: Generally, a cam-action type lock applied to the check rails of a sliding window or at the open edges of a projecting window to pull the check rails tightly together or to seal the sash tightly to the frame, both for security and weather-tightness.
- Sash weights: In older double-hung windows, the concealed cast-iron weights that are used to counterbalance the sash.
- Seat board: A flat board cut to fit the contour of a bow or bay window and installed between the sills and the flat wall surface, providing a seat or shelf space.
- Shims: Wood wedges (often wood shingles) used to secure the window or door unit in the rough or masonry opening in a square, level and plumb position during and after installation.
- Side lights: Tall, narrow, fixed or operating sash on either or both sides of a door to light an entryway or vestibule.
- Sill: Horizontal member that forms the bottom of a window frame.
- Sill course (soldier course): The row of brick, cement blocks or stones laid across the bottom of a masonry opening which lie under the outside edge of the window sill.
- Simulated divided light: A method of constructing windows in which muntins are affixed to the inside and outside of a panel of insulating glass to simulate the look of true divided light.
- Single glazing: Use of single panes of glass in a window. Not as energy-efficient as double glazing.
- Single-hung: A double-hung type of window in which the top sash is fixed or inoperable.
- Slope glazing: Any glazed opening in a sloped roof or wall, such as a stationary skylight or fully operable roof window.
- Solar gain: The process of providing a net heat gain within a structure, over and above the normal heat loss, by passive collection of the sun's heat through windows and other glazed areas.
- Sole plate: The bottom horizontal member in a frame wall. Usually either single or double 2" x 4"s. It is nailed to the deck or rough floor and the studs are nailed into it.
- Stile: The vertical side member of a window sash or door panel.
- Stool: Inside horizontal trim member of a window sash or door panel.
- Stop: A wood trim member nailed to the window frame to hold, position or separate window parts. The stop is often moulded into the jamb liners on sliding windows.
- Stud: Vertical wood framing members which form a frame wall. In normal construction these are eight foot-long 2" x 4"s.
