An upper housing portion has {HEAD ~ an integral pressure blade} for exerting a constant downward force on {TAIL ~ the advancing protective covering} 
An upper housing portion has { HEAD ~ an integral pressure blade } for exerting a constant downward force on { TAIL ~ the advancing protective covering }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL