A hammer of the type having an impact tool driven by pressurized fluid has a hammer body portion with a closed rearward end and an open forward end and a piston longitudinally movably housed within the hammer body portion for striking a tool mounted at the open forward end of the hammer body portion, to thereby impact an object with the tool. The hammer has a fluid valve housed within the closed rearward end of the hammer body portion rearwardly of the piston and in communication with a source of high pressure fluid for driving the piston. The fluid valve has a valve body portion defining an interior chamber and a continuous exterior side wall, and a longitudinal opening in communication with the interior chamber. The valve body has a first body portion and second body portion which is identical to the first body portion and positioned longitudinally in relation thereto within the closed rearward end of the hammer body portion. The first valve body portion and the second valve body portion each have at least one open-sided transverse channel extending from the continuous, external side wall of the wall to the internal valve chamber to thereby simplify and facilitate manufacture of the valve body, and the longitudinal opening and the open-sided transverse channels permit access of pressurized fluid through the valve chamber between the closed rearward end of the hammer body portion and the piston to direct the flow of pressurized fluid entering the valve.