The guide arm has a mount for fitting said machine tool and said housing has at least one top track wheel, at least one side track wheel and at least one oblique track wheel adapted for rolling along the top, side and {HEAD ~ edge} of {TAIL ~ the elongate track}, respectively 
of
The guide arm has a mount for fitting said machine tool and said housing has at least one top track wheel , at least one side track wheel and at least one oblique track wheel adapted for rolling along the top , side and { HEAD ~ edge } of { TAIL ~ the elongate track } , respectively
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH