To create a junction, {TAIL ~ the portion} of material 19 comprises {HEAD ~ a recess} 20 
To create a junction , { TAIL ~ the portion } of material 19 comprises { HEAD ~ a recess } 20
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH