The insert is pushed forward into {HEAD ~ the open jacket} which is pushed away from {TAIL ~ the opening blade} permitting closure by gravity 
The insert is pushed forward into { HEAD ~ the open jacket } which is pushed away from { TAIL ~ the opening blade } permitting closure by gravity
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH