Drawing a line (A) and then draw another line starting in the middle of line A

Question

Im confused at a very basic problem. My aim is to draw a brace, however make the brace look rectangular

I draw a path/line from start A to end B with some lines at the beginning and end to form the end of the bracket. Now i want to draw a line located at the center of the bracket like this:

To achieve this I use a very naive form in creating one node in the midway of the path and another node with a negative xshift and then draw a path connecting these two nodes:

\documentclass{article}
\usepackage{tikz,amsmath, amssymb,bm,color}
\usepackage[active,tightpage]{preview}
\usepackage[margin=0cm,nohead]{geometry}
\usetikzlibrary{shapes,arrows}
\usepackage{tikz-3dplot}
% needed for BB
\usetikzlibrary{calc}
\PreviewEnvironment{tikzpicture}
\begin{document}

\begin{tikzpicture}

\draw(-.7,0,3) to (-1,0,3) to node (mid){mid} node [xshift=-3cm](midleft) 
{midleft} (-1,3,3) to (-.7,3,3);
\draw (mid.center) to (midleft);

\end{tikzpicture}

\end{document}

Is there an easier alternative to draw a path and "using" the centerpoint of this path by say someting like path.center? Many thanks in advance.

Answer 1

Not sure if this is what you need but here is a way to compute the middle point using the calc library or also with the explicit positioning of the node.

\documentclass[tikz]{standalone}
\usetikzlibrary{calc}

\begin{document}

% Solution 1 with calc
\begin{tikzpicture}
\coordinate (A) at (-0.7,0,3);
\coordinate (B) at (-0.7,3,3);
\coordinate (M) at ($(A)!0.5!(B)+ (-0.3,0)$);
\coordinate (L) at ($(M)+ (-0.5,0) $);
\draw (A) --++ (-0.3,0,0) -- (M) ;
\draw (B) --++ (-0.3,0,0) -- (M);
\draw (M) -- (L);
\end{tikzpicture}

% Solution 2 with midway node positioning
\begin{tikzpicture}
\coordinate (A) at (-0.7,0,3);
\coordinate (B) at (-0.7,3,3);
% Option pos=0.5 can be replaced by midway
\draw (A) --++ (-0.3,0,0) --++ (0,3,0)  node[pos=0.5,inner sep=0pt,outer sep=0pt](M){} -- (B);
\draw (M) --++ (-0.5,0,0);
\end{tikzpicture}
\end{document}