rod 150 when the inner gripping unit 208 engages opening 204 of the outer portion 202 in one embodiment the inner gripping unit 208 includes a slit not shown extending along one side of the inner gripping unit 208 to allow the diameter of the inner gripping unit 208 to compress when the inner gripping unit 208 is in the opening 204 in another embodiment the opening 204 is tapered such that the diameter of the opening is larger where the rod 150 enters the gripping unit 156 and smaller where the rod 150 exits the gripping unit 156 the inner gripping unit 208 has a height that is smaller than the height of the outer portion 202 the inner gripping unit 208 includes an opening 210 that is concentric with the opening 204 in the outer portion 202 the opening 210 is sized such that the rod 150 fits into the opening 210 when the inner gripping unit 208 is not inserted into the outer portion 202 and the inner gripping unit 208 compresses onto the rod 150 when the inner gripping unit 208 is threaded into the opening 204 in the outer portion 202 and tension is applied when.