The Anatomy of a Double Hung Window

August 23, 2014

Before you start shopping for replacement double hung windows, you should familiarize yourself with the terminology. With a basic understanding of the components that make up a double hung window you will be able to communicate your needs and preferences to the window repair company more clearly and avoid any confusion.

Double Hung Window Parts ListWindow frames and window sashes of double hung windows can be constructed using a variety of materials including wood, vinyl, aluminum, clad wood, or steel. Refer to the illustration and glossary to learn about the basic anatomy of a double hung window:


The board below the window stool on the interior of the home is referred to as an apron. This piece of trim covers the gap between the window frame and the drywall.


The window casing is the finishing trim that covers the gap between the window frame and the structural framing of the house.

Lower Sash:

This is the lower, moveable, portion of a double hung window.


Window muntins are the strips of wood that form a grid to support the small window glass panes. On newer windows this may be decorative only. Mutins are sometimes referred to as grills.


The small segments in the grid of a double hung window sash are called panes. These small panes are held in place in the upper and lower sashes by mutins. Newer style double hung windows are more likely to have one larger pane of glass in each sash and the mutin will only be used to change the appearance of the windows.


The horizontal support member of the sash is called a rail.

Sash Lock:

The sash lock is the latch that locks the upper sash and lower sash together to secure the window.


The window sill of a double hung window is the lower part of the frame. It is angled downward towards the exterior of the home to shed water away from the window.


The vertical support member of the sash is called a Stile.


The window stool of a double hung window is the lower, interior board which resembles a shelf.

Upper Sash:

This is the upper portion of the window that can be raised and lowered, although it is much more common for home owners to raise the lower sash to allow fresh air into your home.

If your older double hung windows are in disrepair; contact the for a FREE no-obligation quote. The experts at One Source Renovation can inspect your windows and assess your needs. Contact Us today.