%%
%% The LaTeX Companion, 3ed
%%
%% Example A-3-17 on page II-667 in "Rule boxes".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{207.0pt}

\newcommand\sample{ Some text for our page
 that might get reused over and over again.}
%StartShownPreambleCommands
\usepackage{calc}   % \sample as before
%StopShownPreambleCommands

\begin{document}
\ldots \sample                      \par
\nointerlineskip \vspace{5.8pt}
\rule{\linewidth-2\parindent}{0.4pt}\par
\nointerlineskip \vspace{5.8pt}
A following paragraph. \sample
\end{document}