%%
%% The LaTeX Companion, 3ed
%%
%% Example 8-4-18 on page I-623 in "Adding border lines".
%%
%% 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{159.0pt}

%StartShownPreambleCommands
\usepackage{lipsum,tcolorbox}  \tcbuselibrary{skins}
%StopShownPreambleCommands

\begin{document}
Text before the boxed paragraph.
\begin{tcolorbox}[enhanced,frame hidden,
    interior hidden,top=0pt,bottom=0pt,boxsep=0pt,
    borderline west={3pt}{0pt}{blue,dotted},
    borderline west={2pt}{4pt}{black}]
  \lipsum[1][1-2]
\end{tcolorbox}      \ldots{} and text after.
\end{document}