The Woodgrain Millwork 11/16" x 3-1/2" x 96". Medium Density Fiberboard S4S moulding can be used for a wide variety of projects. Medium Density Fiberboard 1x4 S4S moulding is great for constructing cabinets or bookcases. Some S4S mouldings can be used as balusters to support hand rails. S4S is also a great addition to many moulding combinations.