and vinyl phenolic resins epoxy resins and polyimide resins it is desirable that the fiber resin ratio be about 50 60 50 40 v v it is particularly advantageous if the bar is produced from a carbon fiber composition this gives an extremely light product of density 1 45 kg dm 3 the temperature coefficient of expansion is negligibly small so that even at higher operating temperatures there is substantially no longitudinal expansion the placement of the floating plug is illustrated in fig1 which represents the view along line 12 12 showing how plug 857 is held by plug holder 855 in preform 858 and how the threads 852 pass around plug 857 holder 855 is an upright stanchion having a horizontal bore plug 857 is a wedge like prism having an upstream rod bolted into the bore of stanchion 855 in other embodiments the outline of plug 857 and the opening in preform 858 can be altered to produce a guide bar of various cross sections this sector is illustrated in yet further detail in fig1 which shows not modified plug 857a plug 857a has two opposing rectangular notches to produces shelves in the guide bar as illustrated in fig8 10 again plug 857a is held by plug holder 855 web 853 and fibers 852 and 852a are laid around the plug 857 with fibers 852 lying on the outside of said web 853 and fibers 852a on the inside of said web the placement of said fibers in said web within bar 801 is also shown web 853 can be laid in a saddle like shape around the plug 857 web 853 is closed on itself to enclose plug 857 in preform 858 web 853 thereby becomes a laminate for reinforcing the guide.