\documentclass{article}

\usepackage{geometry}
\usepackage[dutch]{babel}
\usepackage{parskip}
\usepackage{amsmath,amssymb}
\usepackage{graphicx,subcaption}
\usepackage{xcolor}
\usepackage{adjustbox}

\geometry{
	paperwidth=9cm,
	paperheight=7.5cm,
	margin=0.0cm,
    paperheight=4.5cm
}

\begin{document}

Blokje: \rule{5pt}{5pt}

Lijntje: \rule{5cm}{0.5pt}

Horizontale lijn: \hrule

Rood lijntje: \textcolor{red}{\rule{5cm}{0.5pt}}

Stippellijntje: Mijn naam is \leaders\hbox{.}\hskip 4cm\relax{}

Geavanceerd: Mijn naam is \leaders\hbox{%
    \rule{4pt}{0.5pt}\kern 2pt\relax
    \rule{8pt}{0.5pt}\kern 2pt\relax}%
\hskip 4cm\relax{}

Ruit: \adjustbox{rotate=45}{\rule{5pt}{5pt}}

\end{document}