Modern heavy duty sledge hammers come with 10 to 20 pounds (4.5 to 9.1 kg) heads. Sledge hammers usually require two hands and a swinging motion involving the entire torso, in contrast to smaller hammers used for driving in nails. The combination of a long swinging range, and heavy head, increase the force of the resulting impact.
Sledge hammers are often used in destruction work, for breaking through drywall or masonry walls. Sledge hammers are also used when substantial force is necessary to dislodge a trapped object (often in farm or oil field work), or for fracturing stone or concrete. Another common use is for driving fence posts into the ground.
They were and still are commonly used by blacksmiths to shape heavy sections of iron.