Anatomy of a Window
Stiles: Stiles are the major vertical supports of the frame of the window sash. They are located on the sides of the windows.
Sash: The sash is the frame that consists of the rails running along the top and bottom and the stiles on the sides. This is what holds the glass in place.
Muntins: Also known as ‘the grids of the windows’, muntins can be decorative and just snap into place over the glass; or they can help hold the glass in place, dividing the glass into sections often referred to as lights.
Muntins are installed on the outside or inside of the glass, or both. Sometimes, they are mounted between two panes of glass, especially on thermal-insulated windows. Windows of this type with the inside-mounted muntins are easier to clean than windows with muntins on the outside of the glass.
Apron: Apron refers to the horizontal board attached to the wall under the windowsill or stool.
Interior Casing: It is the horizontal and vertical moulding that surrounds the entire window. It covers the space between the window and the wall. It can be installed inside or outside the house and provides a finished look.
Jambs: These are the side pieces that form the window frame and hold the sash that holds the glass. They run vertically from the top of the window to the bottom.
Rails: Rails are the horizontal pieces that connect the stiles or vertical pieces of the window. They help hold the glass in place.