Brick mould: The part of the exterior of a window that is designed to cover the small gap between the frame and the exterior siding. It is typically made of wood, wood composite, aluminum or PVC and received its name because brick was once the most common exterior facade or facing.
Traditionally, brick mould was made of wood, which insulates well and can be easily painted. Over time, however, exposure to water and sun can cause it to rot and crack. For maximum durability, it must be maintained with regular cleaning and painting.
Brick mould can also be aluminum-clad, which makes the surface extremely durable. It cannot be painted, but contemporary window manufacturers like Marvin provide a variety of profiles and colors to choose from and the result is a window that needs significantly less maintenance.