What is the bottom of a window frame called?

The bottom of a window frame is called the sill plate. The sill is a vital component of the window, serving as the horizontal support at the bottom of the frame. It helps to direct water away from the window and prevents moisture from entering the structure. Proper installation of the sill is crucial for the window's functionality and longevity since it acts as a barrier against water infiltration and provides support for the window unit.

The sill plate is specifically designed to withstand exposure to the elements, and its design often includes a slight slope to ensure that water drains away effectively. In addition to its practical functions, it also contributes to the overall aesthetic of the window installation. Understanding the role of the sill plate is important for anyone working in construction or window installation, as it directly relates to building integrity and weatherproofing.