Window Frame Parts, Diagram and Terminology

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Experts in Sash Windows Repair & Restoration, Timber Windows & Timber Doors in east midlands

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Sash Windows Refurbish specializes in providing repair and restoration services for wooden windows and doors in the UK, as well as various types of carpentry. During the process of fulfilling orders, we utilize a range of tools and paints, including saws, sprays, primers, resins, and adhesives. With more than 20 years of experience in carpentry, we have tested and used various brands and types of work tools, making us well-equipped to offer helpful advice on selecting the right tools and paints for your needs. Read more ...
Wood window diagram

Window Frame

The window frame serves as the structural support for the entire window. It consists of several key components, each with a specific function.


The sill is the bottom horizontal part of the frame, providing a base for the window. It prevents water from entering the interior and supports the entire structure.


The head is the top horizontal part of the frame, providing structural support to the upper portion of the window.


The jambs are the vertical sides of the frame, supporting the window and connecting the sill to the head.


The apron is a decorative moulding attached to the wall beneath the sill, enhancing the window’s aesthetic appeal.

Casing and Trim

Casing and trim add finishing touches to the window frame, concealing gaps and enhancing the overall appearance.

Window Glass

Beyond the frame, understanding the different components of the window glass is equally important.


The pane refers to a single sheet of glass within the window frame.


The sash is the movable part of the window that holds the glass pane. It can be opened or closed for ventilation.


Mullions are vertical or horizontal dividers between individual window units. They provide structural support and add aesthetic appeal.

Grilles or Muntins

Grilles or muntins are decorative elements that divide the window into smaller sections, enhancing its visual appeal.

Check Rail

The check rail is the horizontal bar in a double-hung window where the upper and lower sashes meet.

Ancillary Parts

Apart from the main components, there are additional parts that play essential roles in a window’s functionality.

Weep Hole

Weep holes are small openings at the bottom of the window frame that allow water to drain out, preventing water buildup.

Weather Stripping

Weatherstripping seals gaps around the window, preventing drafts and enhancing energy efficiency.


Balances are mechanisms that help in the smooth operation of sliding windows. They provide support and ensure easy movement.


Screens are protective layers made of mesh or other materials that keep insects out while allowing airflow.

Window Film

Window films are thin coatings applied to the glass surface to enhance privacy, reduce glare, and improve energy efficiency.

Unique Window Parts

Beyond the common window components, some windows have unique features catering to specific needs.

Insulated Glass Windows

Insulated glass windows are designed for energy efficiency, consisting of multiple panes with special features.


Argon is a gas-filled between the glass panes in insulated windows, enhancing insulation.


Spacers are materials placed between glass panes, maintaining the appropriate gap and preventing condensation.

Casement Windows

Casement windows have specific parts catering to their unique design.

Lock Handle

The lock handle is a mechanism used to secure casement windows, ensuring they are tightly shut.


The operator is a crank mechanism that allows the casement window to open and close smoothly.

Window Glass

Different types of glass are used for specific purposes, enhancing safety and energy efficiency.

Laminated Glass

Laminated glass consists of multiple layers, providing strength and safety. It holds together when shattered, preventing sharp shards.

Tempered Glass

Tempered glass is heat-treated to enhance its strength. When broken, it shatters into small, blunt pieces, reducing the risk of injury.

Low-E Glass

Low-E (low emissivity) glass has a special coating that reflects heat while allowing light to pass through, improving energy efficiency.

Each component plays a crucial role in the window’s functionality and aesthetic appeal. Whether you’re considering traditional windows, insulated glass options, or specialized designs like casement windows, having a grasp of these terms empowers you to choose the right windows for your home.


What is wood around windows called?

The wood around windows is commonly referred to as window casing or window trim. It serves both functional and decorative purposes, enhancing the appearance of the window.

What is the seal around a window called?

The seal around a window is known as weatherstripping. Weatherstripping is used to create a barrier against drafts, moisture, and insects, ensuring energy efficiency and maintaining a comfortable indoor environment.

What is used to seal around window frames?

To seal around window frames, a variety of materials can be used, including caulk, silicone sealant, or foam sealant. These materials are applied to fill gaps and cracks, preventing air and water infiltration, and improving insulation.

About the author

Glen Ramsey, who presently holds the positions of customer support and content manager, is a cherished member of the Sash Window Refurbish team. He is in a unique position to provide advice on all questions pertaining to the renovation of historic windows because he has a wealth of experience in all elements of window renovation, dealing with clients regularly and assisting them in choosing the best window-related course of action. He oversees the creation of information for all of our platforms in his capacity as content manager, including web content and other materials. Glen has witnessed the whole gamut of Sash Window Refurbish's window restoration activities, from our work on significant listed Georgian homes to a wide variety of smaller-scale private residential projects.


My technician Andrew replaced all my sash windows that had rotten sills. Accessing the rotten sills was not an easy task. He explained to me what needed to be done in order to fix the problem. He is a great person and I’m happy that he was the one who did the job. He is reliable, tidy, friendly and very professional. I highly recommend him.



I hired Andrew and Alex a while back to repair my damaged sash windows. They were was very considerate and very patient as he did his job. A few days ago, I had another problem with one of my sash lock keys and I called him again to come and fix the problem. I’m very impressed that Liam responded quickly and he not only fixed the problem but he also gave me a spare key. What a great after sales service!

Alan W.


I’m very impressed with the new windows that Andrew installed and also the reconditioning job that he did on other sash windows. The quality of his work is by far more superior than what we got when we hired another company a few years back. We will certainly hire him again if any window work arises

Kelly (Sleaford)


Our decorator referred us to Andrew because some of the work needed a window expert. Andrew together with our decorator did a fantastic job. The work was done efficiently and to the highest standards. Andrew is understanding, committed and very professional. I recommend him without any hesitation.

Steaven Reader


Alex did a great job in fixing windows in our terraced house. The windows were broken, frames damaged and the wood was also rotten. Alex's job was high quality and he did it pretty fast. I was also very impressed that he was considerate of my son’s asthma condition and maintained cleanliness. Top work.



Andrew just recently replaced three sash windows in my Edwardian house. He also repaired and replaced some sills and draught proofed three windows. In addition to that, he also did some carpentry work. What I like the most about Liam is that he did a clean job. He is very professional and always updated me about the timescales and costs. He also did his job with minimal disruptions. I highly recommend him.

Cris M.