Abstract: A maually operated tool or driver for Allen head screws in which clamping jaws are reciprocated to and from a clamping position by turning of a knurled sleeve. The jaw clamps against a hexagonal operating rod, which can be slid into position through a passageway extending from end to end and through the tool body. This enables the rod to be applied to the tool from either end and militates against the necessity of a predetermined length for the rod. The operating rod fits the socket of the Allen head screw for tightening or loosening it. Flats on the working end of the clamping jaws flatwise engage the side of the rod for insuring against relative turning movement between the rod and the jaws.