\documentclass{article}
\usepackage{german}
\begin{document}

\newsavebox{\warning}
\sbox{\warning}{\setlength{\fboxrule}{0.25mm}\setlength{\fboxsep}{1.5mm}%
\fbox{\parbox{10cm}{\large Vertical placement of minipages and parboxes can
   lead to surprising results which may be corrected by the use of dummy
   lines.}}}

\begin{center} \usebox{\warning} \end{center}
\end{document}