Window Panel

Window Terminology (k-z)

Window Terminology
Keeper:

The hook-shaped piece of hardware that it is mounted on the inside sash stile of a casement window in which the sash lock engages.
Knocked-down:

Not assembled. Parts for a window frame pre-manu¬factured for assembly later on a job site.
Label:

A projecting molding by the sides and over the top of an opening.
Label stop:

Ornamental projection on each end of a label, sill, or sill course. Often takes the shape of a gargoyle or other decorative carving.
Labeled window:

Windows bearing fire-rating labels of Underwriters’ Laboratories (UL).
Laminated glass:

Similar to the construction of car windshields, this technique sandwiches a piece of transparent film or plastic between two panes of glass. Typically used for safety reasons because of its resistance to shattering. Also reduce noise transmission to the interior.
Lancet window:

Tall, narrow window with a pointed-arch top, often with leaded diamond shaped lights; characteristic of Gothic architecture.
Lattice window (also lozenge):

Window with glazing bars set diagonally.
Lead light (also lead glazing; stained glass): Window with small panes of glass set in grooved rods of cast lead or came. The glass may be clear, colored, or stained.
Lift:

A handle or grip installed on the bottom sash rail of a double-hung window to assist in the raising or lowering of the sash.
Light (also lite):

A window; a pane of glass within a window. Double-hung windows are designated by the number of lights in the upper and lower sash, as in 6-over-6.
Lintel:

Horizontal member (wood, steel, or stone) over a window opening to support the weight of the wall above. A header.
Loop window (also Balistraria):

A long and narrow vertical opening, usually widening inward, cut in a medieval wall, parapet, or fortification for use by archers. Modifications appear in Roman¬esque Revival architecture.
Low-E Glass:

A term used to refer to glass which has low-emissiv¬ity due to a film or metallic coating on the surface of the glass. Usually constructed of dual, sealed panes of coated glass filled with pure inert gas to block ultraviolet heat, for cooling purposes, while reflecting room heat back into the room for heating purposes.
LVL:

Laminated Veneer Lumber – A combination of many pieces of veneered lumber glued together to give added structural capabilities. Often used in window or door frames.
Masonry Opening:

The space in a masonry wall left open for the window or door.
Meeting rail (also lock rail):

One of the two horizontal members of a double-hung sash which come together. A check rail.
Meeting stile:

The vertical member in a pair of stiles, as in abutting casement windows.
Mold stone (also jamb stone):

A stone that serves as a window jamb.
Mortise:

A slot or rectangular cavity cut into a piece of wood to receive another part.
Mortise and tenon:

A strong wood joint made by fitting together a mortise in one board and a matching projecting member (tenon) in the other.
Mullion:

A vertical member (usually wood or metal) to structurally join two window or door units.
Muntin:

Vertical or horizontal bars used to separate glass in a sash into multiple lights. Often called a grille.
Nailing Fin:

A vinyl or aluminum extension attached to the frame of a window or door which creates a positive seal be¬tween the window and the framed wall. Acts as an additional barrier against air and water leakage. Screws or nails are fastened through the fin to hold the unit in the opening.
NFRC label:

NFRC stands for the National Fenestration Rat¬ings Council. This non-profit trade group sets energy standards for windows - the NFRC label shows everything you need to know about the window you’re

considering.
North-light roof:

Sawtooth roof with north-facing clerestory windows.
Ogee curve (also ogee molding):

Reverse flex curve commonly found in window moldings and trim pieces.
Operable window:

Window which can be opened for ventilation.
Operator:

A metal arm and gear attached to a window which al¬lows for easy operation.
Palladian window:

A large, arch-top window flanked by smaller windows on each side.
Panel:

Usually refers to the glazed panel or panels in a door frame.
Parting slip:

A thin wood strip separating the sash weights in the weight box of each jamb of old double-hung windows.
Parting stop:

A vertical strip on each jamb that separates the sash of a double-hung window.
Picture window:

Large fixed windows.
Pivot window units:

Window units in which the sash hardware is located near the midpoint of the stile or rail to permit sash rotation.
Prime sash:

Balanced or moving sash of a window unit.
Prime window:

Window with single or multiple glazing. A storm sash may be installed.
Projected window:

Awning type window that swings either inwards or outwards at the top or the bottom. The window usually may be cleaned from the inside.
Quarrel:

A diamond- or square-shaped glass piece set diagonally. A medieval term for small panes of glass set diagonally in Gothic windows.
Queen Anne window:

A window with small glass windows or lights arranged in various forms, usually only on the upper sash. Appeared l870s.
Rail:

Horizontal member of a window sash or door panel.
Reglet:

Plastic or wood molding put in a concrete or masonry opening for a uniform groove for a spline-type gasket to hold window glass.
Reversible extension blind stop:

An extension blind stop that is rabbetted to receive l/2 or 25/32-in. sheathing.
Rough Opening:

A framed opening in which the unit will be installed.
R-Value:

The measurement of resistance to heat transfer in a material. The higher the R-Value, the greater the insulation value.
Sash:

Framework of stiles and rails in which the glass of a window or door is set.
Saddle bar:

Light steel bar placed horizontally across a window to stiffen leaded glazing.
Saddle bead:

Glazing bead for securing two panes.
Sash lock:

A lock applied to the window to pull the sash tightly against the frame (casement) or to pull the check rails together (double-hung) in order to seal the sash from weather and for security.
Single-hung window:

Window similar to double-hung window, except the top sash is stationary.
Seat board:

A flat board cut to fit the contour of a bow or bay window and installed between the sill and the wall surface, providing a seat or a shelf space for plants, etc.
Shading coefficient:

Decimal value which is the solar gain of a window, divided by the solar gain for a clear single-glass

window of the same size. The shading coefficient of clear, double-glazing is about 0.85 to 0.9.
Side light: A fixed, often narrow glass window next to a door opening or window opening.
Sill: Horizontal member at the bottom of the window frame.
Simulated divided lights: A method in constructing windows or doors in which muntins are fixed to the inside and outside of the insulated glass panel to simulate the look of a true divided light. Modern Divided Light® in EAGLE terminology.
Single glazing: Use of single panes of glass in a window sash or door panel. Not as efficient as double glazing.
Single-hung window: Window similar to double-hung window, except the top sash is stationary.
Slide-by window: Windows which slide horizontally.
Smartwindow: Generic term that refers to windows with switchable coatings to control solar gain.
Solid frame: Window frame made from a single piece of lumber.
Sound-insulating glass (also sound-resistive glass): Double glass fixed on resilient mountings and separated so as to reduce sound transmission.
Splayed window: Window unit set at an angle in a wall.
Stacked windows: Combined grouping of awning, casement, or non-operative windows to form a large glazed unit.
Stile: Vertical member of a window sash or door panel.
Stile Lug or Horn: One of two extensions of the sash stiles to support the upper sash of a double-hung window.
Storm clip: Device attached to the muntin of a metal sash to stop the pane from moving outwards.
Stool: An interior trim on a window which extends the sill and acts as a narrow shelf. Often seen on double-hung window.
Stop: A wood trim member nailed to a window frame to hold, position or separate window parts.
Tandem lock: A locking system which secures the window at two locking points by the operation of one lever.
Tempered glass: Special heat-treated, high-strength safety glass which shatters into pebble-sized particles and not in slivers.
Tenon: A rectangular projection cut out of a piece of wood for insertion into a mortise.
Thermal break: A thermal insulating barrier between two thermally conductive materials.
Transom joint: Horizontal member separating a door from a window panel above the door, or separating one window above another.
Transom: Small window located above a door or another window.
Top hung-in window: An awning window pivoted at the top and with the bottom swinging-in.
Transom (also transom bar):

Horizontal member separating a door from a window panel above the door, or separating one window above another.
Triple glazing:

Three panes of glass with two air spaces between, com¬monly consisting of an insulating glass with a separate storm sash. Also available in an insulating window in a single frame.
Triple window:

Generally refers to any tripartite group of windows with square heads. Found on Colonial Revival houses. Units suggest Palladian windows but are less expensive to construct.
U-Value:

Measurement of heat transfer through a given mate¬rial. The lower the U-Value, the better the insulation value.
Venetian window:

Same as Palladian window.
Vertical sliding window:

One or more sash that move in a vertical direction.
View sash:

Picture window with the lights divided by muntins.
Venting unit:

A window or door that operates or opens for ventilation.
Wash cut:

Beveled cut in a stone sill to divert water.
Water drip:

Molding sometimes used on exterior surfaces of an in-swinging casement sash to prevent water from being driven over the sill.
Weather-stripping:

A strip of resilient material applied to the perimeter of the sash and/or frame of a window or door to minimize the potential for water and air infiltration.
Weep cut (also drip cut):

Groove in the underside of a horizontal board or masonry unit which projects beyond the wall service below to prevent water from moving back toward the wall surface.
Yoke:

Head window jamb in a box window frame.
Yorkshire light:

Window with one or more fixed sash and a horizontally moving sash.
Windload:

The force exerted on a surface by moving air.

About the Author

S&K Roofing, Siding and Windows is Maryland's leading company in roofing and maintenance-free home exteriors. Family-owned and operated since 1980, S&K Roofing, Siding and Windows provides high-quality exterior home workmanship and customer service that is among the best in the industry. We offer maintenance-free home exteriors including roofing, siding, windows, doors, gutters and downspouts, custom trim/wrap, and decks.

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CM 690 II Side Window Panel