with reference to the figures , an particularly to fig1 - 3 , there is shown a preferred external fixation assembly 100 which includes a frame composed of arcuate members 10 having a pair of connecting rods 12 adjustably coupled to a peripheral portion of the arcuate members 10 through one or more holes 30 . the frame is depicted as being disposed around proximal and distal portions 201 and 200 of a fractured tibia . the proximal portion 201 is fixated with a plurality of wires or half - pins ( not shown ) which are attached to the proximal arcuate member . the distal portion 200 is fixated to the distal arcuate member through a separate set of pins ( also not shown ) which can be attached at retaining means 14 . fig1 also illustrates a preferred scheme for measuring the distance from the central axis 101 of the bone to the cortical plate . it is essential that a about equals a 1 so that the bone mends correctly . this can be accomplished in the preferred embodiment shown in fig2 and 3 by using a series of locating indicia which can provide a visible contrast on film when exposed to x - ray radiation . in the preferred embodiment 100 , the arcuate members 10 include a top surface 24 , a bottom surface 28 , an internal radial surface 26 , and an external radial surface 22 . the preferred locating indicia include marks on the inner and outer radial surfaces 26 and 22 . preferred marks include geometrical shapes and lines , such as dots 18 , triangles 19 , short slits 17 and longer slits 16 . these markings form a two - dimensional pattern on x - ray film which can readily and accurately provide measurements so that the central axis 101 is aligned properly . the marks can be added to existing fixation devices and can be removable , for example , if applied a tape or paint . this can be accomplished , for example , through careful manipulation of the frame members , whereby a is adjusted to approximately equal b and c , and a 1 can be adjusted to approximately equal b 1 and c 1 , with the result being that a 1 equals b 1 plus d , plus c . other ways of centering the preferred apparatus 100 along the central axis 101 of the bone is to measure from the lateral edge of the proximal and distal portions 201 and 200 of the bone fragments to the edge of the upper and lower rings 10 . fig4 and 5 demonstrate still another preferred embodiment of this invention , a pair of modified arcuate members 110 and 111 are provided for use in an fixation apparatus 100 . these arcuate members are disclosed as being two - piece ring sections of about 180 ° in circumference , having a plurality of radially spaced holes 130 . in an important improvement of this embodiment , a series of protruding lug portions 112 are provided along the periphery of the arcuate members 110 and 111 . these protruding lug portions 112 comprise through - holes 120 for disposing connecting rods , or , alternatively , retaining means for holding wires and half - pins . in one preferred embodiment , the protruding lug portions are disposed at symmetrical locations along the arcuate members 110 and 111 , for example , at equal 45 ° radial spacings . it is relatively important that the protruding lug portions 112 be located at the outer perimeter of the arcuate members 110 and 111 as close as possible to the points where half - pins or wires are attached to the arcuate members so as to avoid the development of unnecessary torque along the arcuate members 110 and 111 . the disclosed lug portions 112 are applicable to any close support system , such as rings , partial rings , triangles , squares , arcs , etc ., and also to open systems having similar shapes for various orthopedic purposes . ( such shapes are also usefully employed with the x - ray indicia and the assembly marking aspects of this invention ). these protruding lug portions are very efficient in increasing compressive force on aligned bones without significantly increasing the weight of the fixation assembly . in a further embodiment of this invention , described in fig6 and 7 , a ring assembly 150 is provided having a plurality of marks 152 , 154 and 156 for identifying the placement of connecting rods and retaining means for half - pins and wires . during an operation , the arcuate members of the ring support assembly 150 are connected with connecting rods , like those described in fig1 at preferred symmetrical distances along the perimeter . in order to place the connecting rods in a correct position , the holes 135 on both rings 150 must be connected in perfect alignment . most physicians count the holes in order to align the rings before placing connecting rods , which is very time - consuming . the described ring assembly 150 is equipped with a series of internal numbers 154 , external numbers 152 , and triangular symbols 156 . alternatively , various symbols such as stars , circles , triangles or other designs could be used to denote the holes 135 , and on other placement positions between the holes . the numbers and symbols are spaced to provide a degree of symmetry in the placement of the assembled external ring members of the support . for example , it is known that the connecting rods should be mounted at 90 ° spacings along the ring assembly 150 . this can be accurately measured on the ring assembly 150 of fig6 by employing the holes marked with a small triangle and an &# 34 ; 8 &# 34 ; and by also employing the two holes at the zero and 180 ° positions . this invention also contemplates making the assembly markings with x - ray contrast indicia so that both assembly and x - ray location can be accommodated with a single set of markings . from the foregoing , it can be realized that this invention provides improved fixation devices and methods for fixating bones . these devices allow for more accurate alignment of the central axis of broken bones , permit greater compressive forces to be applied to bones undergoing therapy and assist physicians in assembling complicated orthopedic assemblies . although various embodiments have been illustrated , this is for the purpose of describing and not limiting the invention . various modifications , which will become apparent to one skilled in the art , are within the scope of this invention described in the attached claims .