How to remove vertical margins when opening an environment (`multicols`)?

Question

When I compile

\documentclass[a4paper]{article}
\usepackage[a4paper, left=5mm, right=5mm, top=4mm]{geometry}

\begin{document}

\noindent\hfil\rule[0mm]{200mm}{.1pt}\hfil
\leftskip4em\rule{.1pt}{150mm}{}

\end{document}

I get

where the horizontal line and the vertical line are connected, as I want. When I introduce a multicols environment in order to may write text at the right of the vertical column and I compile it

\documentclass[a4paper]{article}
\usepackage[a4paper, left=5mm, right=5mm, top=4mm]{geometry}
\usepackage{multicol}
\setlength{\columnsep}{-17cm}

\begin{document}

\noindent\hfil\rule[0mm]{200mm}{.1pt}\hfil

\begin{multicols}{2}

\leftskip4em\rule{.1pt}{150mm}{}

\columnbreak
\textbf{Lorem ipsum}

\end{multicols}

\end{document}

I get

so the horizontal line and the vertical line become disconnected.

How can I solve this issue? Is it possible I open \begin{multicols} without adding the space between the horizontal and the vertical line? Or may I write Lorem ipsum text at the right of the vertical line placed as it is without using multicols and having this issue?

Thank you!

PS: If I do (as suggested for text at first column of page 3 of https://ctan.javinator9889.com/macros/latex/required/tools/multicol.pdf)

\documentclass[a4paper]{article}
\usepackage[a4paper, left=5mm, right=5mm, top=4mm]{geometry}
\usepackage{multicol}
\setlength{\columnsep}{-17cm}

\begin{document}



\begin{multicols}{2}
[
\noindent\hfil\rule[0mm]{200mm}{.1pt}\hfil
]

\leftskip4em\rule{.1pt}{150mm}{}

\columnbreak
\textbf{Lorem ipsum}

\end{multicols}

\end{document}

I get an error:

Paragraph ended before \@rule was complete. [\noindent\rule[0mm]{

Answer 1

See, if the following solution gives what you like to achieve:

\documentclass[a4paper]{article}
\usepackage[a4paper, left=5mm, right=5mm, top=4mm]{geometry}
\usepackage{multicol}

\begin{document}

\noindent\hfill\rule{200mm}{.1pt}\hfill
\hspace*{4em}\rule{.1pt}{150mm}

\vspace{-150mm}
\leftskip 4em \begin{multicols}{2}
\textbf{Lorem ipsum}

\columnbreak
\textbf{Lorem ipsum}

\end{multicols}

\end{document}

Edit: Means of used instructions/commands in above MWE are:

• Space \hspace{<distance>} add horizontal space after some previous object. If there is no object (for example, just text border) than you need to use `\hspace*{} for inserting space before following object.
• Space \vspace{<distance>}, has the same features, but in vertical direction
• \hspace*{4em}\rule{.1pt}{150mm} draw vertical rule with height 150 mm in distance of 4em from left text border. It also introduce vertical space of this amount.
• \leftskip is TeX primitive which determine distance of paragraph from the left text border.
• Command \vspace before multicolumn move start of the multicolumn above for length of vertical rule

This solution is quite rude. Unfortunately, it is not clear, what intention of this rules. Better (more consistent) result probably can be achieved for example by use of tcolorbox with defined top and left border line only.