The technique used to sharpen stones for knives, spears, and arrowheads is known as flint knapping. Today these stones serve as evidence of the Native American hunters who were here as long as 10,000 years ago.
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Additional Links:
The University of Iowa provides a written description of Flint Knapping
https://archaeology.uiowa.edu/flintknapping-0
The Cleveland Museum of Natural History provides a demonstration of Flint Knapping.