Window sill

A window sill (also written as windowsill or window-sill) is the surface at the bottom of a window.

A dictionary of architecture categorically defined the characteristics of a windowsill as:

1. The lowest form of window casement. Windowsills hold pieces in place and slope downward to drain water. In a well hung window, the lower sash rests on the chin;
2. The horizontal piece below a window unit in masonry construction or in wood framing. The window sill of the window frame sits on the window sill of the wall opening;
3. The lowermost, interior trim work on a window;
4. Meets the dictionary definition of a shelf "A flat, usually rectangular structure composed of a rigid material, such as wood, glass, or metal, fixed at right angles to a wall or other vertical surface and used to hold or store objects."