I'm pretty sure its a roller/grinder (though you probably know better than me). You feed barley from the top where it goes between two rollers and pops out the other side as rolled barley. As I said, its run off the PTO shaft of a tractor. Your talking about at least 250 HP driving it!!!! (of course you can control the amount of power with the tractors throttle, but I'm just trying to get across the point that its a fair bit of machinery) I've never paid it much mind (its usually the job I do before I head home/to the pub), but I think I'll give it a closer look the next time I'm there.