%%
%% The LaTeX Companion, 3ed
%%
%% Example 4-1-19 on page I-271 in "The placement of the item label or item text".
%%
%% 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{153.0pt}

  \tolerance=2000

%StartShownPreambleCommands
\usepackage{enumitem}
\SetLabelAlign{right}{\setlength\fboxsep{0pt}%
                      \framebox[\labelwidth][r]{\strut#1}}
%StopShownPreambleCommands

\begin{document}
\noindent Some text to show the left margin.
\begin{itemize}  \item The default.  \end{itemize}
\begin{itemize}[labelindent=17pt,labelwidth=!]
\item No visible difference as label protrudes.
\end{itemize}
\begin{itemize}[labelindent=17pt,itemindent=!]
\item  This results in \texttt{itemindent} becoming
  positive so the paragraph text moves to the right.
\end{itemize}
\begin{itemize}[labelindent=17pt,labelsep=!]
\item Overprint of label and text because
 \texttt{labelsep} becomes negative.
\end{itemize}
\end{document}
