only one spring arm has a cutout see fig4 b where cutouts a a u2032 are equal the operation of this embodiment is similar to that described above in reference to fig4 a as both spring arms 286 286 u2032 will be displaced by an equal amount upon initial installation of the bone fixation rod as with the embodiment discussed above in reference to fig4 b the overall strength of the spring arms 286 286 u2032 may be maintained or even increased as compared to the embodiment described above in reference to fig4 a again by increasing the overall cross section of the spring arms such as by making the spring arms wider cutouts a a u2032 may in an alternate embodiment be of different size or shape providing spring arms 286 286 with unequal spring constants it is noted that in addition to the arcuate cutouts u201c a u201d u201c a u2032 u201d depicted in fig4 b and 4 c numerous other configurations may be employed to produce spring arms which flex varying amounts during installation of the fixation rod 100 for example providing spring arms having different geometric shapes and or widths spring arms incorporating stepped thicknesses or combinations of single or multiple interior or exterior cutouts fig7 shows a u201c stacked u201d bone pin locking assembly which comprises one pin vise portion 1 with two associated fixation rod clamps 50 such a stacked assembly permits the surgeon to provide an additional stabilizing force connected to a second.