\parindent=0pt
par1\par
par2\par
\leftskip=10pt
par3\par
par4\par
\setbox0=\vbox{%
\begin{calstable}
\colwidths{{100pt}}
\brow
 \cell{c}
 \nullcell{ltr}
\erow
\brow
 \cell{c}
 \nullcell{lbr}\spancontent{c}
\erow
\end{calstable}
}
\showthe\wd0
\box0
par5\par
par6\par
\showthe\leftskip
