Holes are drilled to enable {HEAD ~ the selective coupling} of a ball mount and a lynchpin to {TAIL ~ a drop bar} 
to
Holes are drilled to enable { HEAD ~ the selective coupling } of a ball mount and a lynchpin to { TAIL ~ a drop bar }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL