Ice studs look like hex-head sheet metal screws, but they have hardened steel heads, often with sharp points on each corner. Use a nut driver to screw two or three studs into each tire lug. A bag of 1,000 studs costs about $50. You can install studs on all four wheels and still run your ATV at prudent speeds. The disadvantage, of course, is that you'll need to remove the studs in spring, or change tires.