The yarn is fed through a hole in the wall of the tube from {HEAD ~ a groove} on {TAIL ~ the outer surface} 
The yarn is fed through a hole in the wall of the tube from { HEAD ~ a groove } on { TAIL ~ the outer surface }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL