The Van Mark TrimCutter is used to slit aluminum, steel and copper for residential siding, roofing, window and gutter installation right on your Van Mark Brake. The Trim Cutter rides on the top lock bar on all Van Mark Brakes. Designed to protect Van Mark brakes from potential hinge damage from use of utility knives. The rotary knives make consistent cuts giving factory edges every time. Its unique four point track bearing system and low profile grip ensures the tool does not ride off the tracks.