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