{HEAD ~ Another system} allows an operator to vary the width of a mark from {TAIL ~ an initial dimension} 
{ HEAD ~ Another system } allows an operator to vary the width of a mark from { TAIL ~ an initial dimension }
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL