A picket fence and rail mounting system that is easily transformable by the consumer into a variety of aesthetic styles is provided. The system comprises at least an upper and a lower elongate rail. Each rail has a hollow interior defining a substantially I-shaped cross-section including at least a first slot and a second slot. A plurality of pickets are transversely slidable through openings in an upper surface of the rails and a channel in a lower surface. The pickets each have at least a first notch or indentation near a first end and a second notch or indentation near a second end. The distance from the first end to the first notch or indentation is preferably shorter than the distance from the second end to the second notch or indentation. An elongate retaining rod slidable within at least one rail cooperates with a notch or indentation on each picket to secure the picket to the rail. Rather than the retaining rod, spring clips, threaded fasteners or the like may cooperate with a hole in each picket to secure the picket to the rail. The pickets are invertible, such that they extend a distance x or a distance y above the upper rail depending upon whether the first or second notch or indentation or hole engages the retaining rod or other fastening member. Finials and decorative inserts may be secured to the fence to provide more aesthetic styles. Further, the upper rail is invertible, wherein a smooth cap may be secured to the upwardly facing surface of the upper rail, providing the fence with a smooth upper end having no protruding pickets.