One of the last major categories of stone tool to be invented, around the end of the last Ice Age in the Palaeolithic. A flat, heavy cutting tool of stone or metal (bronze) in which the cutting edge is parallel to the haft and which might have the head and handle in one piece. Its main function was for woodworking (hewing, cleaving, or chopping trees) but it was also used as a weapon of war, as the battle-ax. There are many forms of ax, depending on the different materials and methods of hafting. The word ax is now used instead of celt. "Hand-ax" is used to denote the earlier implement which was not hafted. In Mesolithic times stone axes were usually chipped from a block of flint and could be resharpened by the removal of a flake from the end. In the Neolithic axes were polished and often perforated to aid hafting. Axes are now usually iron with a steel edge or blade and fixed by means of a socket in the handle. Smaller lighter ones are called hatchets.