Answer:
Tools have always been made with materials that were available at the time. In prehistoric times, tools were made from simple things, since that is what was available at the time. Most tools were made from rock, shell, bone and wood.
Stone tools are most representative of the times, since we still find evidence of those today. The stones most often used were chert, flint, chalcedony, quartzite, jasper, and obsidian. These rock types, when struck with another rock, piece of antler, or bone, will fracture or break in a characteristic pattern called a conchoidal fracture. This creates a rock fragment called a flake. If fractured correctly, the flake can be used as a knife or tool, since the edge is as sharp as a modern razor blade.
With the the continual flaking of flint, a knife or arrowhead could be fashioned that was sufficient to kill game, till the soil or even chop down trees.