A drive shaft locking mechanism including a locking structure in the form of a gear which is secured to an input shaft of a rotary tool, a retractable interlocking mechanism which selectively couples to the locking structure, and a directional control mechanism coupled to the interlocking mechanism, controlling its movement. The locking structure comprises at least one engageable surface and a means for securing the locking structure to the input shaft. The interlocking mechanism includes a locking element slidably disposed within a tubular channel and selectively extensible therefrom at the urging of the directional control mechanism, to engage the locking structure along an engageable surface.