Some cleaver knives come with a hole in the blade – you will spot it in one of the corners. Some others do not have it. The hole is there to hang the knife on the wall. Decades or centuries ago, butchers could not hang their knives by their handles due to the risk of cutting something. Imagine walking inside a dark room and slicing your ear off because of an invisible knife.
More and more butchers requested knives to have small holes, so they would hang by their blades instead. Today, the modern kitchen has more sophisticated storage opportunities, so the hole is slowly losing its popularity.