Enlarging lenses are designed to work with a greater distance in front of them than behind, so they may give better results at magnifications greater than life size if they are mounted on a reversing ring.
Reversing the lens exposes the rear element that is protected when the lens is mounted normally. You can provide it with some protection by adding a short extension tube to act as a makeshift lens hood; an old manual tube will do. You can also buy special adapters that allow a filter or a lens hood to be attached to the rear of a lens.
Schneider make helical focusing mounts, extension tubes and camera adapters for some of their range of enlarging lenses. Details can be found at Macro System Accessorie, Jos. Schneider Optische Werke.