

\showoutput
\showboxdepth3

\documentclass{scrartcl}
\usepackage{kantlipsum}
\begin{document}
\kant*[7]

\begin{figure}[!htbp]
  \leavevmode\smash{\rule{1pt}{26pt}}\kant*[7]
\end{figure}

\leavevmode\smash{\rule{1pt}{26pt}}\kant*[7]
\end{document}