 In a backing fire, the fire moves against the wind. Backing fires exhibit the slowest rate of speed and the lowest intensity. Backing fires are always used at the beginning of a prescribed fire to create a black line. These black lines are formed on the downwind side of the site and enlarge the established fire lines. They add an extra layer of protection and help prevent the fire from escaping. Backing fires typically have a slower rate of spread, shorter flame length and less intensity than other techniques. Because backing fires move slower and tend to linger, they exhibit more complete fuel consumption than other techniques. These characteristics can also lead to damage or killing trees by cooking the root collar of the tree.