Also known as pressure flaking, this is a useful skill that enables you to make knives, arrow tips and scrapers etc.
Basically, it involves breaking up certain kinds of rocks to create sharp edges or other, which in turn may be refined further according to your needs.
Once the desired characteristics are obtained, you may affix the stone to a handle to make a hammer or an axe if you'd like.
A stone that is fashioned into an arrow tip can be installed on a straight branch or sturdy plant stem to make an arrow. Spear heads may be made as well.
stone adze is a tool that can be used to cut and shape wood. You can even take down a tree with it.
Obsidian, chert, flint, sandstone and other conchoidal fracturing stones and even glass may be used. It must be able to support a strike and possess qualities that will produce flaking. The angle of the strike and pressure among other things will determine the result.
A stone with the right shape can be used as you found it to use as a hammer. Be creative with what you have to work with.
You can make primitive tools of all sorts. Besides rocks and wood, bones can be used as well. Small and sharp implements can be made with bone such as arrow heads and awls to make holes for sewing.
Here are some links to help you learn more about flint knapping.
4. Wildwood Survival - Survival Hand Vice
Here is a link to help you learn more about primitive tools.
Have a look at the Videos page as well for more information on the subject.