Which part of the window frame is located at the top?

The part of the window frame that is located at the top is referred to as the head jam. In window terminology, the head jam is the uppermost piece of the frame that supports the window and provides structural integrity. It serves as one of the boundaries for the window opening and is crucial in protecting the interior from weather elements by directing water away from the top of the window.

Understanding the function of the head jam is essential in evaluating a window's design and performance. Other components of the window frame serve different purposes; for instance, the sill is located at the bottom and acts as a ledge for moisture runoff, while jams (or side jams) run vertically along the sides of the window. The bottom rail is a component of the sash, which holds the glass and is located, as the name suggests, at the bottom of the window itself. Recognizing these distinctions helps in understanding how windows are assembled and how they function as part of a building's exterior system.