5 inches. Do not use a tow behind or riding mower to cut materials on slopes at more than a 15 degree angle. If using a tow behind mower on land that slopes less than 15 degrees, ride up and down the hill, not across the face. Driving across the face of a slope greatly increases the potentially deadly chances that your mower and attached ATV will roll over. If you have control over what is planted on a slope, opt for a ground cover other than turf. Finally, if your plot has experienced thick growth, mow it over twice and don’t overexert your mower.