\documentstyle[chbars]{article}
\begin{document}
\catcode`\@=\letter
\catcode`\_=\letter
\hsize=2in \vsize=3in
\tolerance=10000 \hbadness=10000
\def\nl{\unskip \hfill \break}
\def\np{%
   \ifhmode  \vadjust  \fi
   {%
      \vfill \eject
      }%
   }

\tracingall \tracingonline=0
\tracingparagraphs=0

\section{test}

\changebarwidth=1.1pt       % Set the default size to 1.1pt
Zeile 1

\beginchange[2pt]           % Test giving an option
Zeile 2
\mark{Mark 1}%
\write 16{Ausgabe 1}%
Zeile 3
\endchange

Zeile 4%
\mark{Mark 2}%
\mark{Mark 3}

\beginchange[0.4pt]         % Now try another size
Zeile 5
\write 16{Ausgabe 2}%
Zeile 6
\endchange

Zeile 7
\beginchange
Zeile 8
\write 16{Ausgabe 3}%
Zeile 9
\endchange
Zeile 10
\beginchange
Zeile 11
\write 16{Ausgabe 4}%
Zeile 12
\endchange
Zeile 13
\beginchange
Zeile 14
\write 16{Ausgabe 5}%
Zeile 15
\endchange
Zeile 16
\beginchange
Zeile 17
\write 16{Ausgabe 6}%
Zeile 18
\endchange
Zeile 19
\beginchange
Zeile 20
\write 16{Ausgabe 6}% Test of newpage
\np
Zeile 21
\endchange

\chbarRighttrue           % do the margins on the right
\changebarwidth=3pt
\beginchange
Zeile 22
\endchange

One last paragraph before the new section.

\beginchange\section{test2}\endchange

Last section and quit

\end{document}