%%
%% The LaTeX Companion, 3ed
%%
%% Example A-3-20 on page II-669 in "Manipulating boxed material".
%%
%% 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{183.0pt}
%StartShownPreambleCommands
\newsavebox{\myboxa}\newsavebox{\myboxb}
%StopShownPreambleCommands

\begin{document}
\sbox{\myboxa}{inside box a}
\savebox{\myboxb}[2cm][l]{inside box b}
  x1x \usebox{\myboxa} x2x \usebox{\myboxb} x3x
\savebox{\myboxb}[2cm][r]{inside box b}
  \par
  x1x \usebox{\myboxa} x2x \usebox{\myboxb} x3x
\end{document}