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Key stocks are removable steel bars or wedges that transmit torque from components like gears, sprockets, and sheaves to a shaft. They serve as keys since they lock the components to the shaft by affixing them in the key seat. Woodruff keys are semi-circular in shape that fit in shafts with a semicircular pocket. Parallel sunk keys on the other hand are the most common key stocks that have a square cross-section. They are placed in a longitudinal slot in both the shaft and the component. Key stocks are available in both metric and imperial standards.