Window Terminology

Regarding Window Terminology: Often, there is more than one term used to describe a particular part or style of window. This portion of our website does not claim to be “the final authority” on such terms – it merely defines the term Clear Creek Windows uses. In general, when more than one term is in common usage for a particular part or style of window, Clear Creek Windows attempts to use the most common term used in the market area it generally operates in.


I. Main Parts of a Window





Sash Approximately 1.5” x 1.5” (40mm x 40mm), the sash is the part of the window that is attached to the glass and moves with the glass.
Stile The approximately 1.5” x 1.5” vertical parts of the sash.
Rail The approximately 1.5” x 1.5” horizontal parts of the sash.
Meeting Rail For a single or double hung window (see “Window Styles” section), the meeting rail is the part of the window comprised of the top rail of the lower sash and the bottom rail of the upper sash.
Glass Stop The small moulding approximately 1/2” x 1/2” (12mm x 12mm) that holds the glass into the sash. For windows built without sashes (picture windows – see “Window Styles” section), the glass stop is the similar moulding that holds the glass into the frame.
Frame Comprised of the head, jamb, and sill that together form an opening in which the sash fits.
Head Horizontal component that forms the top of the window frame.
Jamb Vertical components forming the sides of the window frame.
Sill Horizontal component that forms the bottom of the window frame.


Vertical Mullion When two or more window frames are joined together “side-by-side”, the frame members that form the vertical “posts” are no longer called “jambs”; they are called “vertical mullions”.
Horizontal Mullion When two or more window frames are stacked one on top of the other, the frame members that are a combination of the sill of the upper window and the head of the lower window are called “horizontal mullions”.
Muntin Solid piece of material that separates two pieces of glass within the same sash.