{HEAD ~ A reinforcing agent} is placed between {TAIL ~ each} of the barbs of the connector  
is placed between
{ HEAD ~ A reinforcing agent } is placed between { TAIL ~ each } of the barbs of the connector
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH