Are you looking into continuous line furling systems? Diego Sosa of sail-world.com has some useful diagrams to help explain the two systems.
“Top-down” and “bottom-up” furling are expressions used primarily for continuous line furling systems using a torsional cable/rope, around which the sail furls.
As opposed to a traditional foil furling system, used on cruising boats, where the jib/genoa is hoisted in a luff groove in the aluminium foil and the sail furls around the full length of the foil. Read More