The "Grinder" is a manual line retriever for F3J winch lines. It's also a great way to store your lines and keep them tangle and kink free. Our grinder system has a removable drum, and a geared drive to help pull your lines quickly and easily.
One of those simple little things that makes life easier.
Above Pic shows spare drum available here: http://www.soaringusa.com/Grinder-Drum.html