Trying to Add a Separator in the Table of Contents

Question

I would like to add a line segment of specified length in the Table of Contents to separate two distinct portions. (I have search this site, but could only find an example to add a full-length horizontal line.)

I am surprised at my difficulty in accomplishing this because \rule{1.25in}{.15mm} works fine within the document itself. However, when I try to add the following, I get an error message:

\addcontentsline{toc}{\rule{1.25in}{.15mm}}

Consider the working example:

\documentclass[12pt]{book}

\usepackage{tocloft}
\renewcommand\cftchapafterpnum{\vskip 12pt} %set space after each Chapter in the Table of Contents
\renewcommand\cftsecafterpnum{\vskip 8pt}  %set space after each Section in the Table of Contents
\renewcommand\cftsubsecafterpnum{\vskip 8pt}  %set space after each Subsection in the Table of Contents


% Centering Table of Contents
\renewcommand{\cfttoctitlefont}{\hfill\Huge\bfseries}
\renewcommand{\cftaftertoctitle}{\hfill}


\begin{document}
\addtocontents{toc}{\protect\thispagestyle{empty}}
\tableofcontents

\addcontentsline{toc}{chapter}{Chapter 1}
\addcontentsline{toc}{chapter}{Chapter 2}
\addcontentsline{toc}{chapter}{Chapter 3}


\addtocontents{toc}{\vspace{\normalbaselineskip}}
%\addcontentsline{toc}{\rule{1.25in}{.15mm}}
\addtocontents{toc}{\vspace{\normalbaselineskip}}

\addcontentsline{toc}{chapter}{Next Part of the Table of Contents}
\end{document}

which produces the output

However, when I run the code with the \addcontentsline{toc}{\rule{1.25in}{.15mm}} command, I get the error message "Argument of \reserved@a has an extra }. \addtocontents".

And the following output results:

Again, I would like to add a horizontal line segment of specified length to the TOC---but everything I've tried so far has failed. Could someone please advise what I am doing wrong and how to correct it? Thank you.

Answer 1

You need to use \addtocontents rather than \addcontentsline and insert a \par after your \rule in order for the ToC contents to be processed successfully.

\documentclass{book}

\usepackage{tocloft}
\setlength{\cftbeforechapskip}{12pt}%set space after each Chapter in the Table of Contents
\setlength{\cftbeforesecskip}{8pt}  %set space after each Section in the Table of Contents
\setlength{\cftbeforesubsecskip}{8pt}  %set space after each Subsection in the Table of Contents

% Centering Table of Contents
\renewcommand{\cfttoctitlefont}{\hfill\Huge\bfseries}
\renewcommand{\cftaftertoctitle}{\hfill}

\begin{document}

\tocloftpagestyle{empty}

\tableofcontents

\addcontentsline{toc}{chapter}{Chapter 1}
\addcontentsline{toc}{chapter}{Chapter 2}
\addcontentsline{toc}{chapter}{Chapter 3}

\addtocontents{toc}{\vspace{\normalbaselineskip}}
\addtocontents{toc}{\rule[.1\normalbaselineskip]{1.25in}{.15mm}\par}
\addtocontents{toc}{\vspace{\dimexpr\normalbaselineskip-\cftbeforechapskip}}

\addcontentsline{toc}{chapter}{Chapter 4}

\end{document}

I moved the \rule up a tad to appear better vertically centered between the two chapter headings. I also used the default tocloft vertical spacing/skips and page styles rather than add that content to the ToC manually. It doesn't really matter that much though.

Answer 2

This will place the line precisely in the middle of a 36pt gap (\baselineskip=12pt).

\documentclass[12pt]{book}

\usepackage{tocloft}
\renewcommand\cftchapafterpnum{\vskip 12pt} %set space after each Chapter in the Table of Contents
\renewcommand\cftsecafterpnum{\vskip 8pt}  %set space after each Section in the Table of Contents
\renewcommand\cftsubsecafterpnum{\vskip 8pt}  %set space after each Subsection in the Table of Contents


% Centering Table of Contents
\renewcommand{\cfttoctitlefont}{\hfill\Huge\bfseries}
\renewcommand{\cftaftertoctitle}{\hfill}


\begin{document}
\addtocontents{toc}{\protect\thispagestyle{empty}}
\tableofcontents

\addcontentsline{toc}{chapter}{Chapter 1}
\addcontentsline{toc}{chapter}{Chapter 2}
\addcontentsline{toc}{chapter}{Chapter 3}

\addtocontents{toc}{\rule[\dimexpr 0.5\ht\strutbox-0.5\dp\strutbox]{1.25in}{.15mm}\vskip 12pt}

\addtocontents{toc}{Next Part of the Table of Contents}
\end{document}