"Trüler" is the German word for the person who works a grape press for wine-making.
Stucki's image has been rendered in strong chiaroscuro, creating an almost carved look to the body of the trüler and the effectively portraying the physicality of the scene - the trüler uses the entirety of his body to push a handle attached to a movable pole. In turn, a rope, attached to a screw press, turns its handle to apply pressure to a platen, crushing the grapes for the juice.