Guide to Parts of a Window (With Diagrams)

Learning more about parts of a window can help you identify the replacement pieces you need. While all windows have a frame and glass panes, different styles have different features. 

Whether you’re buying replacement windows or trying to fix a draft, understanding your window’s components will allow you to make an educated purchase.

Keep reading to learn more about the parts of a window.

Main Parts of a Window

Parts of a Window

The entire window system has components and exterior parts that need replacement over time. It’s crucial to get the hang of the core window parts since each window style is different.

Here’s a list of the essential parts of a window and a breakdown of how they work together.

Window Sash

A window sash fits inside the frame to hold the glass. Sashes also push the window up or down. It comprises stiles (vertical part) and rails (horizontal piece) that house the glass.

Standard home windows have an upper sash, a lower sash, and a check rail. The upper sash is the upper part of a single or double-hung window. For single-hung windows, the upper sash is fixed. The lower sash is adjustable in both windows, and you can move it up to let in air.

A check rail is a horizontal part on a double-hung window where the sash surfaces come into contact. While opening the entire window, the lower rail of the upper sash and the upper rail of the upper sash intersect.

Window Panes

A window pane is the glass part of a window. Glass lets in natural light, seals out drafts, and insulates a house. The glass can be clear or tinted for privacy. Glass varies depending on the number of sheets used.

Multiple panes reduce noise and are more energy-efficient compared to single-pane windows. A glazing compound and an extruded aluminum rail are common window parts that keep the panes in place.


Grilles are parts of a window that divide the glass into four or more sections. Not all windows have grilles. The bars are decorative and make windows appear as multiple panels.

They can be installed in between or on top of the glass. Grilles have horizontal and vertical parts that add structural integrity.

Grille Clips

Grille clips are fasteners for decorative window grilles. Full-surround grilles are detachable and require grille clips to secure them in place. When placed over the glass, full-surround grilles conceal the clips.

Fixed Panel

The section of a window that doesn’t open or close. For a single-hung window, the upper sash is an inoperable panel. Picture windows and most round windows also have fixed panels.

Lift Rail

A lift rail, or lift handle, is an upper part or horizontal section of a window sash. It opens and closes single or double-hung windows.

Stool Cap

A window stool cap is a horizontal trim below the interior sill. It projects outwards by some inches and makes a good window display surface.

Main Parts of a Window Frame

Main Parts of a Window Frame

The window frame is the exterior structure that holds all the panes in place. A window frame consists of the head, jamb, and sill. Together, they hold the window in place.

Windows with multiple glass panes have more parts like spacers and gas fills for insulation. Wood is the traditional window frame material. Modern windows have a frame made of fiberglass, vinyl, or metal.

  • Head – The head is the top horizontal part of the window frame. It aids in strengthening the window frame after installation.
  • Jamb – The jamb is a vertical side of the window frame joining the head and sill. Jambs are inside the framing on both sides of a window.
  • Window sill- A window sill is the exterior wood parts or extruded rigid PVC on the bottom part of the window frame. It sits right below the lower panel of a window.

Other Parts of a Window


You can finish off your window’s exterior frame with a casing. It serves as decorative molding and a seal between the window frame and the wall, blocking any outside air from entering your home.


A transom is a horizontal beam that separates a window frame from an additional window above it. Transom windows fill the space between a window’s frame and high ceilings. Transom windows that can move up and down are popular in bathrooms for ventilation. Modern homes have transoms for aesthetics and natural light.


A mullion is a heavy vertical or horizontal bar separating a window’s two sides. It is a major structural piece that can either be permanently fastened or removable from the frame.


Window installers use weatherstripping to seal the window sash to the frame. Weatherstripping types include foam tape, tubular rubber, felt, and v-strip. Choose a weather stripping that will withstand friction and weather changes. Weather stripping creates energy-efficient windows by blocking potential paths for warm and cold air leaks.


An apron is a decorative trim to finish the area beneath a window sill or a stool. It’s installed against the wall to enhance the window’s appearance. While not always present, you can find aprons on several window types.

Window screen

A screen is a standard feature for most windows today. It is custom-made from plastic, fiberglass, or wire to fit the window opening. When a window is open, screens keep insects, bugs, and dust from entering the house.


Spacers are strips of plastic or metal used to separate double or triple-pane windows. An ideal spacer should support the glass panes and seal in the argon injected between them. It should also repel moisture away from the seals.

In the past, manufacturers used aluminum to make spacers. The spacers were strong yet too rigid, causing seal breakage and foggy windows. Today you can find spacers in different materials, including metal, metal-foam alloys, and plastic.


A reveal is a piece of wood to which the window frame is attached during installation. It is fixed on all sides to support a window. A sill replaces the reveal’s horizontal bottom.


A window’s architrave is a decorative molding that frames the wall around the window. Placing an architrave around your windows improves their visual appeal. Architraves come in both pattern and minimalist designs.

Window Panels

A window panel maintains insulation, lets light in, and blocks unpleasant airflow. Windows have a hinged glass panel, making it easy to operate and control the airflow.

Parts of a Window: Hardware

Hardware refers to the window parts you use to open and secure your windows.

  • Sash lock – The sash lock prevents the window from opening. Double-hung windows have a lower sash and an upper sash. 
  • Locking Mechanism – The locking mechanism offers protection against break-ins. Frames with two or more windows have their locking mechanism on top of the sash. Most windows have sash latches and a lock handle. You want to fix your locking mechanism on a frame made of solid wood for added reinforcement.
  • Balance – A balance is a system with springs to counteract the weight of the sash when opening and closing a window. Window balances are inside the jambs of single and double-hung windows.
  • Ventilation Stop – On the upper sash, there are vent stops. You can move the peg out to stop the lower sash from opening all the way. Pella windows include this feature on their exterior vinyl windows to enhance safety.

Common Window Designs

  • Double Hung Windows – A double-hung window has two sashes: the top sash and the bottom sash. You can adjust both sashes in a double-hung window but only the lower sash in a single-hung window. The vertical side of a double-hung window is wider, allowing you to add multiple panes.
  • Casement Windows – A casement window has a hinged sash that slides out to open via a crank-operated device. Casement windows don’t have a center rail. Unlike standard types, a casement window opens and closes like a door via a mechanical device attached to the sides of the frame. The window casement design is ideal for difficult-to-reach areas like over the kitchen sink.
  • Single-Hung Window – A single-hung window has an upper, fixed sash and a lower, moveable sash. The bottom portion of the window moves up and down, while the top portion does not. Single-hung windows have a lower sash that allows for ventilation. You can open the top sash alone, the bottom sash, or both for better airflow.
  • Awning Window – Awning windows have a top hinge that allows the frame to swing outwards while open. They sit above or below other windows to increase lighting and open space. Awning windows provide ventilation and weather protection since they’re hinged at the top and open outward from the bottom.

Frequently Asked Questions (FAQ)FAQ

Which material is ideal for weatherstripping windows?

A tension seal or a V strip is a durable plastic or metal strip ideal for weatherstripping double-hung or sliding windows. Tension seals are inexpensive and easy to install. Vinyl, which is a little more expensive, is also durable and resistant to moisture.

How much do parts of a window replacement cost?

Location, window materials, glazing type, and window type will affect window replacement costs. Depending on window frame material and glass type, window replacement costs $200 to $2,100 per window, with a national average of $750 per window.

Is it hard to install parts of a window?

Going the DIY way is practical if you have some carpentry skills. Installing many windows is time-consuming, so it’s worth hiring a professional. You’ll also avoid common mistakes that end up ruining the overall aesthetics.

Parts of a Window: Conclusion

Some window elements differ by type. Learning window part names and anatomy before replacing your windows will help you know what to look for.

Each window has different parts, so it’s important to know what you’re buying. Knowing your window’s components and benefits will help you avoid mistakes and settle for one that suits your home.