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November 29, 2019

Anatomy of A Window: What Each Piece Is Called

At Atlas Glass, we find that most people think that window design is all about glass. This is understandable! But the truth is, windows are comprised of numerous parts and accessories, each of which has a definite name and purpose within the window industry that not many know of.

If you’ve been referring to parts of the window as the ‘top bit’ or ‘bottom bit’, you might want to brush up your knowledge on window terminology. Join in for a crash course to learn what each part is called, and the purpose it serves!

Basic parts

Every window has three basic parts – the frame, the sash and the panes.


If you’re looking at your window head-on, the frame is the piece surrounding the window. Frames surround the entire window system and provide support.


The sash is the moveable part, both horizontally or vertically, that holds the glass in place. With casement windows, sashes swing open, on double-hung and single-hung windows, they usually slide up and down to open and close the windows.


In simple terms, panes are the glass. Panes are connected to sash or muntins, which are grid-like bars that feature in some windows. Windowpanes can be single, double or even triple glazed to provide insulation. Double-glazing refers to creating a window that consists of two glass panes separated by vacuum or gas to reduce heat transfer.

The Parts of a Frame

The basics can be broken down even further into the sum of their components. If you delve deeper, you can see that there are innumerable small yet intricate parts that make up a window and assist in its smooth functioning.

Let’s start with the frame. This component of a window can be broken down into three smaller components: the jamb, the sill, and the head. There’s also the casing, which is a very important aspect of window design.


Jambs are the vertical boards that are found between the head and the sill.


Sill is down the bottom, where you can rest your arms if your sitting by the window!


Opposite to the sill, the head is the top horizontal part that forms the top of the frame.


Casing is the decorative frame or moulding that is found around the window to cover the space between the jamb and the wall. Sometimes, it can be seen covering space between two window frames.

The Parts Related to the Sash

While these parts aren’t a part of the actual sash, they do help it to function. The parts included depend on the type of window installed.


The Balance is found right at the center of the window. True to its name, it provides balance as the sash opens and closes. 

Check rail

Usually found on double-hung windows, this is the part where two sashes meet in the middle – the bottom part of the upper sash and the upper part of the bottom sash. 


The Jambliner is a strip that is usually found on the side of the window frame. It gives the window sash a snug fit.


A lift, as suggested by the name, is what makes it possible to raise the window in case of single or double hung windows.

Sash lock

A sash lock is the mechanism that is used to lock single and double hung windows. It is usually located on the operating sash and is used for preventing the sash from opening in its frame.


A stool is the horizontal board on the inside of the window, against the sash.

Reach out to us

Whether you’re refurbishing your house with retrofit double-glazing or getting new timber joinery installed in your brand-new home, You can count on the experts at Atlas Glass. Contact us today for more information.

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