Anatomy Of A Window

Curious about the anatomy of a window? We have put together an illustration of double-hung windows along with the terms that describe the anatomy or parts for replacements or new construction windows. We have also included definitions of applicable terms if you scroll down.

Anatomy Of A Window

anatomy of a window

Definitions Behind Window Anatomy

Horizontal piece/slat of trim beneath the window sill.

Argon Gas
A type of gas that is used to replace the air in double or triple glazes to increase the energy efficiency by decreasing the amount of heat loss.

Center Hung Sash
A sash that is hung or mounted on pivot pins in the center so the sash can be pivoted open in order for easy cleaning.

The fixed part of windows (the perimeter) within which the sash or panes of glass are mounted.

The frame along the top. Also called the header.

Head Expander
U-shaped filler (usually made of vinyl) on the head.

The frame members on each vertical side (similar to the ‘head’ which is the frame member on the top of the window).

Main Frame
The main parts of a frame (the jambs (sides), head (top) and sill (bottom)).

Meeting Rail
Horizontal rails of two opposing sashes that meet when the unit is closed.

Mullion (or Muntin)
Separator (either vertical or horizontal) between two windows.

The horizontal member of a sash on the top or bottom.

The part of windows that contains the panes of glass. It can be fixed to the frame or can be movable.

Sash LockA lock that works by having one portion of the lock on each of the meeting rails of windows (a cam lock on the lower sash and the matching receptacle on the upper sash).

The horizontal shelf that sits along the bottom interior of a frame.

Weep Hole
Small holes in the exterior sill that encourages water to drain.

Related Topics

Window Terminology
Components Terminology
Construction Terminology
Frame Terminology
Installation Terminology