\font\fivett=cmtt10 at 5pt
\setbox0=\hbox{\yoko pF}
-\setbox1=\hbox{\tate\box0}
+\setbox1=\hbox{\tate\copy0}
\fbox{\copy1}
-\unhcopy1\setbox1=\lastbox
+\setbox1=\copy0
{\obeylines\seventt\baselineskip=10pt
\directlua{luatexja.ext_show_node_list(tex.box[1], 'lastbox> ', tex.print)}\par}
\setbox0=\hbox{\yoko \ltjsetwd1=50pt}
\hbox{\inhibitglue\tate}
\hbox{\ltjsetparameter{kanjiskip=0pt}\tate}
+
+\leavevmode\hbox{A}%
+\setbox0\hbox{}%
+\setbox1=\lastbox\the\wd1
\end