\def\e{e e e e e e e e e e e e e e e}
\def\ee{\e \e \e \e \e \e \e \e \e \e \e}
\def\eeee{\ee \ee \ee \ee \ee \ee \ee \ee \ee}
\def\eee{\eeee \eeee \eeee \eeee \eeee \eeee \eeee \eeee \eeee}
\setbox10=\vbox{
  \hsize 6.15in \smallskip \eee \smallskip
}
\setbox11=\vsplit10 to 50pt

\def\getsegment{
  \setbox11=\vsplit10 to 50pt
  \noindent\hbox{\vrule\hskip1em\vbox{\unvbox11}\hskip1em\vrule}\par
}
\def\largesect{
  \getsegment\getsegment\getsegment\getsegment\getsegment\getsegment
}
\splittopskip=0pt
\setbox12=\vbox{
\hrule\par
\largesect\largesect\largesect\largesect
\hrule}
\unvbox12
\bye