tapered as shown in fig1 with these tapers when the nuts are tighten the grip set will be forced to close the gaps 5 between them during grips closing the inner profile of the grips will be seated flatly on the surface of the bars while the bars 39 ribs and grips 39 rib indents will also seated on each other and create interlocking mechanism required in bar connection fig2 b and 2 c show inner surface of a piece of grip set and cross section of a nut 3 in fig2 a for a thread bar with side view 2 e and end view 2 f in fig2 rib pattern textures 21 on each bar are already identical the inner texture of the grip can be designed to duplicate their thread ribs 15 and its picture is shown in fig 2 f since the ends of the self coupling bars from factory may not necessarily be cut at the correct location to fit exactly with that of the grip set the ends of each bar may have to be trimmed see fig5 arrow b b therefore the rib pattern of the connecting bars when they are placed on their adjacent ends are matched with the female rib pattern of the grip set upon connecting the bars both adjacent ends of the bars will be placed equally on the longitudinal length of the grip set as shown in fig6 when the grip set is tightened.