wellhead housing 45 has an axial bore 47 with an upward facing load shoulder 49 wellhead housing 45 is conventional except for the addition of a latching groove 51 which is positioned below load shoulder 49 for receiving retaining ring 43 once retaining ring 43 latches into groove 51 load ring 31 will be held stationarily within wellhead housing 45 in operation the operator will calculate the amount of stretch that he wishes to place in the unsupported portion of casing 13 below wellhead housing 45 in this embodiment the unsupported portion begins at the upper level of cement and extends to the wellhead housing 45 the operator will then secure positioning ring 29 at a particular point along external threads 23 to predetermine the distance between stop shoulder 17 and landing shoulder 41 of load ring 31 load ring 31 will be positioned on running tool 21 with its upper end in contact with the lower end of positioning ring 29 the initial distance from the lower end of load ring 31 to stop shoulder 17 will equal the desired amount of stretch the bias of split inner ring 35 will frictionally hold load ring 31 in place until retaining ring 43 latches in groove 51 the operator lowers the string of casing 13 into the well fig1 shows the running tool.