5. Edge molding. Moldings can be added to almost every part of a cabinet or shelf. This homeowner or designer added molding to the outside edge of the shelving, known as an edge molding. Decorative molding on open shelving not only adds a new design feature, but it can also add a structural element. Some shelving, depending on the span (anything over 36 inches) can bow from weight if it isn't supported correctly. Applying an edge molding to the outside edge of the shelf can prevent sagging.