Abstract: A fastener/shaft locking and adjustment apparatus and locking system which precisely positions, positively locks and avoids slippage of a positive locking nut along an elongated element. The positive locking nut includes a locking spline, an outer knurled cylinder, a rotatable spline, a return spring and a threaded nut. The locking spline includes a key member extending into the passage thereof which is engaged in the channel of the elongated element such that the locking spline does not rotate with respect to the elongated element. The locking spline further includes a first gear along an outer surface thereof which is capable of meshing engagement with a second gear provided along an inner circumferential cavity of the rotatable spline to lock the locking nut at its desired position along the elongated element.