The working of stone by applying force to its surface - by percussion or pressure - to produce a tool. A knapper is one who manufactures stone artifacts, especially by chipping. This technique of striking flakes or blades from a hard, brittle rock, such as flint or obsidian, id done by means of short, sharp blows delivered with a hammer of stone, bone, or wood. Knapping was used to fashion stone tools and weapons, such as blades and arrowheads, in the Harappan culture of the Indus Valley and was also applied to making beads from agate and carnelian.