\def\ltshframe #1#2#3#4{\vbox{\hrule height #1pt%   
 \hbox{\vrule width #1pt\kern 0pt%               
 \vbox{\kern0pt\frame{.3}{#2}{#3}{#4}\kern-#1pt%   
 \kern-.3pt}%                                   
 \kern-#1pt\vrule width 0pt}%         
 \hrule height 0pt}}%                        

\ltshframe{4}{5}{23pc}{\box4}