\documentclass{article}

\usepackage{amsmath}

\usepackage{tikz}

\usetikzlibrary{arrows}

\usetikzlibrary{calc}

\begin{document}

\begin{tikzpicture}[>=latex', node distance=2cm]

\node (Xo) {};

\node [right of = Xo] (S1) {\Large $x$};

\node [right of = S1] (S2) {};

\draw [->,ultra thick,blue] (Xo) -- node[above, black] {$v_1$} (S1);

\draw [->,ultra thick,blue] (S1) -- node[above, black] {$v_2$} (S2);

% Lets draw a line with a blunt end, -|

\draw [-|,ultra thick,blue]

% start in the middle of S2, and move down 2.75 mm

% ($ ... $) notation is used to add the coordinates

($ (S1) + (0mm,-2.75mm) $)

% Now draw the line down by 3mm

% -- means draw to, + means move by

-- +(0,-3mm)

% Now move back to the left of S2

% The symbol -| means draw horizontal then vertical.

% If we used -- instead the line would be drawn

% diagonally to the reaction edge.

% (S1) is the center of the node. But we want the

% blunt end to end below the S1 line and

% half way to the left. The 10mm is half the node

% distance of 2cm, and 1mm is slightly below

% the reaction line.

-| ($ (S1) - (10mm,1mm) $);

\end{tikzpicture}

\vspace{1cm}

\begin{tikzpicture}[>=latex', node distance=2cm]

\node (Xo) {};

\node [right of = Xo] (x1) {\Large $x_1$};

\node [right of = x1] (x2) {\Large $x_2$};

\node [right of = x2] (x3) {};

\draw [->,ultra thick,blue] (Xo) -- node[above, black] {$v_1$} (x1);

\draw [->,ultra thick,blue] (x1) -- node[above, black] {$v_2$} (x2);

\draw [->,ultra thick,blue] (x2) -- node[above, black] {$v_3$} (x3);

% Lets draw a line with a blunt end, -|, using the following coords

\draw [-|,ultra thick,blue]

% start in the middle of x2, and move down 2.75 mm

% ($ ... $) notation is used to add the coordinates

($ (x2) + (0mm,-2.75mm) $)

% Now draw the line down by an additional 3mm

% -- means draw to, + means move by

-- +(0,-3mm)

% Now move back to the left of x2

% The symbol -| means draw horizontal then vertical.

% If we used -- instead the line would be drawn

% diagonally to the reaction edge.

% (S1) is the center of the node. But we want the

% blunt end to end below the S1 line and

% half way to the left. The 10mm is half the node

% distance of 2cm, and 1mm is slightly below

% the reaction line.

-| ($ (x1) - (10mm,1mm) $);

\end{tikzpicture}

\vspace{1cm}

\begin{tikzpicture}[>=latex', node distance=2cm]

\node (Xo) {};

\node [right of = Xo] (x1) {\Large $x_1$};

\node [right of = x1] (x2) {\Large $x_2$};

\node [right of = x2] (x3) {\Large $x_3$};

\node [right of = x3] (x4) {};

\draw [->,ultra thick,blue] (Xo) -- node[above, black] {$v_1$} (x1);

\draw [->,ultra thick,blue] (x1) -- node[above, black] {$v_2$} (x2);

\draw [->,ultra thick,blue] (x2) -- node[above, black] {$v_3$} (x3);

\draw [->,ultra thick,blue] (x3) -- node[above, black] {$v_4$} (x4);

% Lets draw a line with a blunt end, -|

\draw [-|,ultra thick,blue]

($ (x3) + (0mm,-2.75mm) $)

-- +(0,-3mm)

-| ($ (x1) - (10mm,1mm) $);

\end{tikzpicture}

\vspace{1cm}

\begin{tikzpicture}[>=latex', node distance=2cm]

\node (Xo) {};

\node [right of = Xo] (x1) {\Large $x_1$};

\node [right of = x1] (x2) {\Large $x_2$};

\node [right of = x2] (x3) {\Large $x_3$};

\node [right of = x3] (x4) {\Large $x_4$};

\node [right of = x4] (x5) {};

\draw [->,ultra thick,blue] (Xo) -- node[above, black] {$v_1$} (x1);

\draw [->,ultra thick,blue] (x1) -- node[above, black] {$v_2$} (x2);

\draw [->,ultra thick,blue] (x2) -- node[above, black] {$v_3$} (x3);

\draw [->,ultra thick,blue] (x3) -- node[above, black] {$v_4$} (x4);

\draw [->,ultra thick,blue] (x4) -- node[above, black] {$v_5$} (x5);

% Lets draw a line with a blunt end, -|

\draw [-|,ultra thick,blue]

($ (x4) + (0mm,-2.75mm) $)

-- +(0,-3mm)

-| ($ (x1) - (10mm,1mm) $);

\end{tikzpicture}

\vspace{1cm}

\begin{tikzpicture}[>=latex', node distance=2cm]

\node (Xo) {};

\node [right of = Xo] (x1) {\Large $x_1$};

\node [right of = x1] (x2) {\Large $x_2$};

\node [right of = x2] (x3) {\Large $x_3$};

\node [right of = x3] (x4) {};

\draw [->,ultra thick,blue] (Xo) -- node[above, black] {$v_1$} (x1);

\draw [->,ultra thick,blue] (x1) -- node[above, black] {$v_2$} (x2);

\draw [->,ultra thick,blue] (x2) -- node[above, black] {$v_3$} (x3);

\draw [->,ultra thick,blue] (x3) -- node[above, black] {$v_4$} (x4);

% Lets draw a line with a blunt end, -|

\draw [-|,ultra thick,blue] (10mm, -8mm)

-- +(0,6mm);

\node (x) at (10mm,-11mm) {\Large $x$};

\end{tikzpicture}

\end{document}