\documentclass{standalone}
\pagestyle{empty}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}

\draw[thin,->]  (-2,0)--(2,0);
\draw [blue] (-2,-1)--(0,-1) (0,1)--(2,1);
\draw [blue,dashed] (0,-1)--(0,1);



\draw [magenta,yshift=1]  (-2,-1)--(-.5,-1)--(.5,1)--(2,1);
\draw [green,yshift=2]  (-2,-1)--(-1,-1)--(1,1)--(2,1);

\draw [orange,yshift=3]  (-2,-1)--(-1.5,-1)--(1.5,1)--(2,1);






\end{tikzpicture}
\end{document}
