Abstract: In a drill string jar apparatus having an elongated tool body positionable within a drill string, which would also include a latch mandrel movable within a bore of the tool body between a first neutral position and fired up or fired down positions; a substantially continuous channel formed in the interior wall of the tool body, a shoulder portion on the exterior wall of the latch mandrel body for latching into the channel of the tool body when the mandrel is in the neutral position and slots in the wall of the latch mandrel for allowing the mandrel body to flex inwardly sufficiently to disengage the shoulder portion from the channel in the tool body and allow the latch mandrel to move upward or downward within the bore of the tool body depending upon the direction of the force imparted on the mandrel and make contact with the upper or lower end of the tool in order to dislodge a tool below the jar apparatus.