After {TAIL ~ application} of {HEAD ~ individual twists}, two elementary yarns are twisted together to form a strand 
After { TAIL ~ application } of { HEAD ~ individual twists } , two elementary yarns are twisted together to form a strand
OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH