In some instances this can be helpful in actually piecing a core back together from its flakes. So if you find a thin chip of stone with a slightly-thicker bulge on one end, you can be sure that you've found a flake. These often served as actual knife blades, as hide scrapers, or as engraving tools. The scarred nucleus of tool stone that results from flintknapping is called a core. The goal of lithic reduction can be to manufacture an object or objects from either the removed flakes, the core itself, or both.
Cores are, along with flakes, the most obvious evidence of flintknapping.
If a variety of tools, but no flakes or cores, is found at a site, then it's safe to assume that no lithic reduction was occurring at the site. Sometimes the types of cores at a site will, along with the waste flakes found, indicate the type of lithic reduction that was occurring there. Sometimes flakes and core fragments were modified into unifaces. A uniface is a tool that has had flakes systematically removed from one side, producing a sharp edge. Often, the flake scars are tiny, suggesting that they were removed with a very fine point or, occasionally, by the flintknapper's teeth.