As best seen in FIG 6 the guiding rail 105 in cross section has {TAIL ~ a pair} of {HEAD ~ first and second mounting legs} 107, 109 parallel to one another 
As best seen in FIG 6 the guiding rail 105 in cross section has { TAIL ~ a pair } of { HEAD ~ first and second mounting legs } 107 , 109 parallel to one another
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH