Window grilles are narrow strips of wood, vinyl, or metal used to visually separate the glass of a window into “panes” or lites. They are purely aesthetic — not necessary for the structure of the window. When the lines the grilles create are purely horizontal and/or vertical, they are sometimes referred to as grids. But grilles can curve into a gothic shape, intersect in a diamond pattern, and more, creating a look that goes beyond a classic “grid.”