{HEAD ~ The elbow} can have {TAIL ~ two nestable channel sections}, each channel section having a generally C shaped cross section, which may be substantially semi circular 
{ HEAD ~ The elbow } can have { TAIL ~ two nestable channel sections } , each channel section having a generally C shaped cross section , which may be substantially semi circular
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH