%%
%% The LaTeX Companion, 3ed
%%
%% Example 6-1-3 on page I-434 in "Using the \protect \nxLenv  {tabbing} environment".
%%
%% 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
\newcommand\lenrule[1]{\makebox[#1]{%
  \rule{.4pt}{4pt}\hrulefill\rule{.4pt}{4pt}}}
%StopShownPreambleCommands

\begin{document}
\begin{tabbing}
  dd\quad \= \hspace{.55\linewidth} \= \kill
  pc  \> Pica = 12pt       \> \lenrule{1pc} \\
  cc  \> Cicero  = 12dd    \> \lenrule{1cc} \\
  cm  \> Centimeter = 10mm \> \lenrule{1cm} \\
\end{tabbing}
\end{document}