newlengthfigurewidth
newcommandfdash
  {settowidthfigurewidth{9}%
   raisebox{0.6ex}{makebox[figurewidth]{hrulefill}}%
  }

documentclass{article}
newlengthfigurewidth
newcommandfdash
  {settowidthfigurewidth{9}%
   raisebox{0.6ex}{makebox[figurewidth]{hrulefill}}%
  }
newcommandtest
   {noindent
    123456789\
    1234fdash6789\
    - -- fdash ---%
    bigskippar
   }
begin{document}
test
{ttfamilytest}
{tinytest}
end{document}