The process of stone toolmaking is a subtractive process where pieces of stone are progressively removed from the starting piece to achieve the final result.  A stone tool preserves remnants of the very last flakes removed, which intrude into older flake scars, and those into still-older flake scars, and so on.  The sequence of flake removal is recorded in the way the scars intrude into each other.

Some lithic analysts are specially trained to determine the ordering of the scars on a tool, and by reconstructing the scars chronologically—and comparing this to the waste flakes found in association—the analyst can reconstruct in some detail the various steps that were taken to manufacture the tool.

These steps are referred to as the ‘reduction sequence’ or ‘châine opératoire’ for the particular technology.  This is called ‘diacritical analysis’ and involves closely studying the chronological ordering of the scars by assessing tiny clues on the edges of flake scars.