A flanking fire is a fire burning at 90 degrees to the wind or slope of an area. These generally are found at the sides (flanks) of headfires. They do not move as fast or create as much heat as a headfire, although they are much hotter and faster than a backing fire. These fires can be attacked starting from their upwind side and extinguished more readily than a headfire. In a controlled burn these will sometimes be ignited by walking directly upwind with an ignited driptorch. With flanking fires one must use caution because if the wind shifts a bit, or the flank gets ahead of other parts of the headfire, it can also become a headfire. Flanking fires often have interesting formations such as fire whirls.