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