Blasting or blowing stumps was a standard practice for stump extraction in the past. In rural areas and on large sites disrupted by construction, blasting can still be used under carefully controlled conditions. Usually a hole is bored or dug beneath a stump and the blasting charge inserted. In areas away from underground utilities, wells, foundations, and buildings, charges can be set. In the past there was a tendency to use an over-charge of explosives, spewing wood, rocks, and soil many yards. In the blast, the shockwave of the explosion and rapidly expanding gases shear off roots and elevate the stump and soil. The blast heavily compacts the soil below the charge. Carefully controlled and directed explosive charges can be successfully used by certified explosive experts in concert with stump removal specialists. Special training and permits are required to purchase, transport, and use the explosives traditionally used to blow stumps. The extent of clean-up after the explosion can be controlled by using blast mats (like a mat of interconnected old tires) to cover and hold down flying debris.