Steel box graters, flat graters, rasp graters and rotary graters are all different types of vegetable shredders. Manufacturers either stamp or etch square or round holes in the steel that act as teeth to shred the vegetables. Stamped holes produce thick, uniform shreds, while etched holes produce shorter, thinner shreds.
Box graters are the most common, and typically have multiple grating surfaces, including medium and large holes, pinhole bumps, and a mandoline-like slicer. Flat graters are essentially one side of a box grater, typically with only a single size hole, held vertically or horizontally over a work surface. Handheld rasp graters have a long, narrow grating surface, best for smaller shredding tasks. Rotary graters use a cylindrical drum to shred vegetables via a turning mechanism that passes food through sharp metal holes.
The surface of steel graters consist of either stamped or etched holes. Stamped holes are mechanically punched out of a steel sheet, with the protruding side catching the food and forcing it against the edge, shredding it. Manufacturers form etched holes by chemically corroding thin sheets of steel to create fine, super-sharp teeth. Etched holes are sharper than stamped holes and produce thinner shreds.
The shape of the hole determines the quality of the shred. Round holes produce more uniform shreds, with consistent thickness end to end. Square holes produce curly, inconsistent shreds, with thicker middles.