答案1
\documentclass{article}
\usepackage{lipsum}
\newenvironment{signenv}[1]{%
\par
\smallskip
\noindent\hrulefill\ %
\begin{picture}(20,20)(0,0)
\put(10,0){\makebox(0,0){#1}}
\put(0,0){\line(1,1){10}}
\put(0,0){\line(1,-1){10}}
\put(20,0){\line(-1,1){10}}
\put(20,0){\line(-1,-1){10}}
\end{picture}\ %
\hrulefill
\par
\bigskip}
{\par\medskip\noindent\hrulefill\par\smallskip}
\begin{document}
\begin{signenv}{A}
\lipsum[1]
\end{signenv}
\end{document}