Since the pin is symmetrical, its orientation relative to the circuit board is unimportant, which facilitates {HEAD ~ automatic insertion} of the pin into {TAIL ~ the board} 
into
Since the pin is symmetrical , its orientation relative to the circuit board is unimportant , which facilitates { HEAD ~ automatic insertion } of the pin into { TAIL ~ the board }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL