A fragment removed from a larger stone (the core or nucleus) by percussion or pressure, which leaves characteristic marks on both the core and flake called the bulb of percussion. This makes it comparatively easy to distinguish human workmanship from natural accident, but the factor of design must be proved to give certainty. Flakes often served as blanks from which more complex artefacts, or flake tools, could be made. Flakes are difficult to date precisely, such as those from Pulpit hillfort unless associated with other more dateable tools.