One of the three principal design formats for pediments is a rounded form: some portion of a circle. A plain window pediment is a simple arch that mounts with either end aligned with the ends of the breastboard, so that the arch appears to be an extension of the rectangular window below. Plain window pediments are broad arches, less than a quarter of a circle, extending across the wall above the breastboard. While a breastboard can be milled with several steps and a top lip to give the window frame some dimension, a plain window pediment is a basic piece of unadorned moulding curving from corner to corner.

• Standard pediments require one more installation step in the window framing process than pediments with attached breastboards.
  
• Many standard pediments, including plain window designs, are produced today from synthetic materials such as polyurethane or fiberglass.
  
• Synthetic plain window pediments installed above the exterior of a window will match wooden moulding nicely and will resist the impact of weather better than wood will.
  
• Standard pediments in plain window designs can be mounted above any type of window moulding during a remodel. Because there is no attached breastboard a standard pediment will match up with many types of moulding, especially when a simple design such as the plain window is used.
  
• Squaring the window frame and leveling the breastboard are critical when you are mounting a pediment in order that the arch be level.
  
• Pediments are a decorative addition that enhances any home, whether used indoors or out.