When the fork reaches the top of {TAIL ~ the bar} and has thus removed any material impaled upon {HEAD ~ the bar}, it pivots in response to an attached spring back to its initial position wherein it engages the next bar in sequence 
When the fork reaches the top of { TAIL ~ the bar } and has thus removed any material impaled upon { HEAD ~ the bar } , it pivots in response to an attached spring back to its initial position wherein it engages the next bar in sequence
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH