documentclass{standalone}
    usepackage{tikz}
    usetikzlibrary{calc}

    begin{document}
      begin{tikzpicture}
         coordinate (a) at (0,0);
         coordinate (b) at (1,-1);
         newlength{vsep}
         setlength{vsep}{0.5cm}
         coordinate (abovea) at ($(a) + (0,vsep)$);
         coordinate (aboveb) at (b |- abovea);
         node[fill=black,circle,inner sep=2pt] at (a) {};
         node[fill=black,circle,inner sep=2pt] at (b) {};
         draw (a) -- (abovea) -- (aboveb) -- (b);
    end{tikzpicture}
   end{document}