Formatting chapter in memoir

Question

I'm trying to reproduce this chapter heading (Styling my section/chapter) in memoir. This is more or less working with the following code:

\documentclass[11pt,oneside]{memoir}
\usepackage{blindtext}

\makechapterstyle{uno}{%
  \setlength{\midchapskip}{5pt}
  \renewcommand{\chapnumfont}{\Huge\bfseries}
  \renewcommand{\printchaptername}{}%
  \renewcommand*{\chapternamenum}{}
  \renewcommand{\printchapternum}{}%
  \renewcommand{\chaptitlefont}{\Huge\bfseries\scshape}
  \renewcommand{\printchaptertitle}[1]{%
   \hspace*{-0.1\textwidth}\chaptitlefont ##1}
  \renewcommand{\afterchaptertitle}{%
   \vskip -2pt \hspace*{-\marginparwidth}\rule{0.7\textwidth}{5pt}}
   }

 \chapterstyle{uno}

\begin{document}
\chapter{Es war einmal ein Mann}
\blindtext[1]
\end{document}

But my question: Why does the following code:

\renewcommand{\afterchaptertitle}{%
\vskip\midchapskip\hspace*{-\marginparwidth}\rule{0.7\textwidth}{5pt}}
}

leave such a large separation to the rule? As far as I understand, \vskip is creating a new paragraph. But if I use

\renewcommand{\afterchaptertitle}{%
\vskip\midchapskip\hrule}
}

there is no separation at all (only the 5pt of \midchapskip). \rule and \hrule are behaving differently, but I can not understand why and I did not see a good explanation for this.

Answer 1

\hrule is a vertical mode command so in vertical mode stacks directly under the previous thing.

The LaTeX \rule starts with \leavevmode and so is a horizontal mode command and so if used in vertical mode you will get a vertical \parskip space and a horizontal \parindent.

You will see the same behaviour if you compare \hbox{hello} with \mbox[hello}

(Also in your example you have \hspace* in the \rule example which similarly is a horizontal command.)

Perhaps this is closer to your needs

 \renewcommand{\afterchaptertitle}{{%
   \par\offinterlineskip\hbox{\hspace*{-\marginparwidth}\rule{0.7\textwidth}{5pt}}}}