a printing element having {HEAD ~ an impacting surface} at {TAIL ~ its front end} and a driven surface at its rear end 
at
a printing element having { HEAD ~ an impacting surface } at { TAIL ~ its front end } and a driven surface at its rear end
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH