You will find here some explanation about typical terms used in our industry. This will help you get a good grasp and make the right decisions for your projects.


A window unit in which the bottom of the sash swings outward.
A composite of three or more windows, usually made up of a large center unit and two flanking units at 30°, 45° or 90° angles to the wall.
A composite of four or more window units in a radial or bow formation.
A type of external casing which frames windows and doors.
A window unit in which the single sash cranks outward, to the right or left.
Inside casing is a flat, decorative moulding that covers the inside edge of the jambs and the rough openings between the window unit and the wall. Outside casing (or brick mould, above) serves the same purpose, while it also is an installation device through which nails are driven to install the window unit into the wall.
On a double-hung window, the bottom rail of the upper sash and the upper rail of the lower sash, where the lock is mounted.
A generic term referring to any of a variety of window units with one or more curved frame members, often used over another window or door opening.
An aluminum material locked to the outside faces to provide a durable, low-maintenance exterior surface.
A space which protrudes from the roof, usually including one or more windows.
Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits.
A window with two vertical operating sash that slide up and down.
A form produced by forcing material through a die.
An architectural term referring to the arrangement of windows in a wall. From the Latin word, “fenestra,” meaning window. Fixed Non-venting or non-operable.
A metal or plastic strip attached to the outside of the head or side jambs to provide a weather barrier, preventing leakage between the frame and the wall.
Foam material placed in the air space of the insulating glass to enhance the appearance and improve the performance of the window.
Hinged door(s) which have wider panel members around the glass.
A sliding door which has wider panel members around the glass, giving the appearance of a French hinged door.
The glass panes or lights in the sash of a window. Also the act of installing lights of glass in a window sash.
A term referring to window pane dividers or muntins, usually a type of assembly which may be detached for cleaning.
Single or double pane construction made up of laminated glass containing a .090 interlayer.
A combination of two or more panes of glass with a hermetically sealed air space between the panes of glass. This space may or may not be filled with an inert gas, such as argon.
The main vertical members forming the sides of a window or door frame.
In a modern double-hung window, the track installed inside the jambs on which the window sashes slide.Light(also spelled lite) Glazing framed by muntins and/or sash in a window or door.
A common term used to refer to glass which has low emissivity due to a film or metallic coating on the glass or suspended between the two lights of glass to restrict the passage of radiant heat.
The vertical or horizontal divisions or joints between single windows in a multiple window unit.
An interior or exterior casing member to cover the mullion joint between single windows.
A short bar used to separate glass in a sash into multiple lights. Also called a windowpane divider or a grille.
a non-profit organization that provides fair, accurate and credible energy performance ratings for windows and doors.
A large, arch-top window flanked by smaller windows on each side.
Usually refers to the separate panel or panels in a door frame.
The use of casing on all four sides of the interior of a window, replacing the stool and apron at the sill. Also known as full-bound casing.
The pitch of a roof is the degree of the inclination upward from horizontal or flat. It may be expressed in degrees or as the ratio of the number of inches it rises in each 12 inches of horizontal span: 4/12 means the roof rises four inches in every foot of horizontal span.
A mode of operation for ventilating windows which generally means the sash pivots on a central axis and turns 90 or more degrees.
The horizontal members of a window sash or door panel.
The opening left in a frame wall to receive a window or door unit.
The horizontal rough framing member, usually two inches by four inches, which forms the bottom of the rough opening. It is toe-nailed into the jack studs and is supported by cripples.R-ValueResistance to thermal transfer or heat flow. Higher R-value numbers indicate greater insulating value.
A single assembly of stiles and rails made into a frame for holding glass.
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.
Tall, narrow, fixed or operating sash on either or both sides of a door to light an entryway or vestibule.
Horizontal member that forms the bottom of a window frame.
The row of brick, cement blocks or stones laid across the bottom of a masonry opening which lay under the outside edge of the window sill.
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.
Use of single panes of glass in a window. Not as energy-efficient as double glazing.
A double-hung type of window in which the top sash is fixed or inoperable.
Any glazed opening in a sloped roof or wall, such as a stationary skylight or fully operable roof window.
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.
The vertical side member of a window sash or door panel.
Inside horizontal trim member of a window sash or door panel.
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.
wood framing members which form a frame wall. In normal construction these are eight foot-long 2″ x 4″s.
Glass manufactured to withstand greater than normal forces on its surface. When it breaks, it shatters into small pieces to reduce hazard.
A smaller window above a door or another window. A transom joint is also the horizontal joining area between two window units which are stacked one on top of the other.
A sash glazed with three lights of glass, enclosing two separate air spaces.
A term that refers to windows in which multiple individual panes of glass or lights are assembled in the sash using muntins.
A measure of heat transmission through a wall or window. The lower the U-Factor, the better the insulating value.
A window or door unit that opens or operates.
A material or device used to seal the openings, gaps or cracks of venting window and door units to prevent water and air infiltration.
A short bar used to separate glass in a sash into multiple lights. Also called a muntin or a grille.

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