to wall contact downhole in the production of fluids utilizing a sucker rod string in addition when the bars are used with a certain percentage of sucker rods a greater efficiency and thus reduction of friction is accomplished in production of the fluids downhole application_number US 53787083 A description as illustrated in fig1 and 2 the sinker bar of the present invention is generally designated by the numeral 10 and normally has an overall length l of 24 feet the bar 10 has a square cross section for a substantial portion of its length lengths l1 l2 and l3 as illustrated in fig1 and 2 have a square cross section normally length l1 will be inserted first into a well bore as illustrated in fig1 and 2 only the square surface areas 15 16 and 17 associated with l1 l2 and l3 respectively are illustrated it being understood that such surfaces represent flat surfaces of those portions of the bar having a square cross section as further illustrated in fig1 adjacent each end 20 and 21 are machined female threads 22 which extend inwardly as shown by the dotted lines into the ends 20 and 21 respectively with each end 20 and 21 being a flat surface a bevelled area 23 is provided around the outer periphery of such flat surfaces 20 and 21 the bevel or scallop area 23 of the surfaces 20 and 21 permits a pressure interlocking of surfaces on adjacent bars when bars are mated end to end with suitable pin to pin connection not shown a pin pin assembly technique can also be used with standard couplings it is to be understood that the square.