Window Parts, Explained

Window frames, sashes, muntins…what do they all mean? Whether you’re looking to get your windows repaired or shopping to get them replaced, it helps to understand the different parts of a window.

Let’s have a look at each part of a window. We explain the parts and their importance, below.

Window pane

A window pane is the plate of glass filling the window frame. Windows can be single-pane, double-pane, or triple-pane, meaning that they can have one, two, or three panes of glass within the same frame.

Window panes are key to the efficiency of a window. Double and triple-pane windows (which have insulating gas between each pane) are significantly more energy efficient than the single-pane version. Homeowners with old, single-pane windows may want to consider upgrading to lower their energy bills and increase their home’s value.


A window’s frame is the outermost part of the window, the part that holds all the rest together within the wall. It’s made of the head, the jamb, and the sill.

Head: The head is the top, horizontal part of the window frame.

Jamb: The jamb is the vertical side of the window frame.

Sill: This is the bottom, horizontal part of the window frame. It usually protrudes out like a kind of shelf in the home’s interior.

The frame, as you can probably already guess, is critical to the window’s performance. If there are problems with the frame, the window may let in water, get drafty, or even become structurally unsound. (Because of this, it’s extremely important to have experienced window technicians install your windows.)


This is the part of the window that holds the panes in place. It’s made up of the horizontal and vertical frames surrounding the glass. If you have an operable window (i.e. any window that can be opened), this is the part that is moved when you open the window. The sash is made of the stiles and rails.

Stiles: The stiles are the vertical parts of the sash supporting the window panes.

Rails: The rails are the horizontal parts of the sash supporting the glass.

A window’s sash is another important part that heavily influences how well the window functions. If the sash is warped or damaged in some way, your window may leak or let in drafts. In addition, you might find it impossible to open or close your window.


This is the horizontal board attached to the wall directly under the window sill.


Muntins are the grids of a window. They can be purely decorative (put in place on top of the glass) or they can divide the glass into sections and help hold it in place.


This is a part that is found on awning and casement windows. It is a crank that allows you to open and close the window.

Extension Arm

This is the part of the window, attached either to the rail or stile, that extends or contracts (thereby opening or closing the window) when you crank the operator.


The latch is the locking device on the window, located on the rail or stile of the window. It also helps to seal the window, making it important for energy efficiency.


This is the decorative molding surrounding the window frame. It’s usually on the inside of the house. Depending on the style of the home and the homeowner’s taste, the casing can be modern or elaborate.

Whew, that’s a lot of window terminology! If you have more questions about window parts, types of windows, or other topics, feel free to give us a call or check out our blog.