A safety rail for a flatbed trailer including a track that is engaged adjacent an edge of the flatbed trailer and a plurality of post holder assemblies engaged with the track. The post holder assemblies are selectively movable along the track between an operational position and a storage position. When the safety rail is in the operational position, the post holder assemblies are spaced a distance apart from each other and, when in the storage position, the post holder assemblies are in tongue-and-groove interlocking engagement with each other. A post is engaged with each of the post holder assemblies and a cable is threaded through an aperture in each of the posts. The post holder assemblies include one or more wheels which engage the track and roll therealong as the safety rail is moved between the operational and storage positions.