In contrast to other kitchen knives, the cleaver has an especially tough edge meant to withstand repeated blows directly into thick meat, dense cartilage, bone - and the cutting board below. This resilience is accomplished by using a softer, tougher steel and a thicker blade, because a harder steel or thinner blade might fracture or buckle under hard use.
Cleavers are primarily used for cutting through thin or soft bones and sinew. With a chicken, for example, it can be used to chop through the bird's thin bones or to separate ribs. Cleavers can also be used in preparation of hard vegetables and other foods.
Cleavers are not used for cutting through solid, thick and hard bones,instead a bone saw.