Fastening tool for driving a fastener such as a staple into a substrate a predetermined distance. The tool includes a housing and a driver reciprocally mounted in the housing and moveable with respect to the housing, the driver having a driving surface for engaging a fastener such as a staple. A magazine assembly is associated with the housing for positioning and aligning the fastener in the path of the driver so that when actuated, the driver strikes the fastener and forcibly ejects it from the magazine into the substrate to a predetermined extent so as to adjust or control the holding power of the fastener about the object.