The {\tt pspolygon} is a great way to create arbitrary shapes!

\begin{verbatim}
\pspolygon(x0,y0)(x1,y1)(x2,y2) ... (xn,yn)
\end{verbatim}
You can provide an array of coordinates that will render a polygon \cite[10]{pstricks}


You can add an aribitray number of coordinates onto the end of the command, and produce any shape you'd like!

\begin{center}
\begin{pspicture}(-3,-3)(3,3)
\pspolygon(-1,-1)(-1,2)(1,0)(-2,0)(1,1)
\end{pspicture}
\end{center}

which can be produced with the following code:

\begin{verbatim}
\begin{pspicture}(-3,-3)(3,3)
\pspolygon(-1,-1)(-1,2)(1,0)(-2,0)(1,1)
\end{pspicture}
\end{verbatim}


\begin{center}
\begin{pspicture}(0,-3.5)(8,2)


\rput(0,0){$x$}
\rput(7.2,0){$y$}
\rput(5.5,-1.25){$z^{-1}$}


\rput(3.65,-2){$\alpha$}
\rput(1.5,-2.5){$H$}

% plus or minus for adder
\rput(2.1,-0.5){$-$}
\rput(1.45,0.35){$+$}

\psframe(1,-3)(6.5,1)

\pspolygon(4,-1.5)(4,-2.5)(2.5,-2)

\psline{->}(0.25,0)(1.5,0)
\psline{->}(1.75,-2)(1.75,-0.25)
\psline{->}(5.5,-2)(4,-2)
\psline(2.5,-2)(1.75,-2)
\psline{->}(2,0)(7,0)
\psline(5.5,-1.7)(5.5,-2)
\psline{->}(5.5,0)(5.5,-0.75)

\psframe(5, -1.7)(6,-0.75)

\pscircle(1.75,0){0.25}
\psline(1.5,0)(2,0)
\psline(1.75,0.25)(1.75,-0.25)


\end{pspicture}
\end{center}

Which can be produced with the following \TeX:

\begin{verbatim}
\begin{pspicture}(0,-3.5)(8,2)
\rput(0,0){$x$}
\rput(7.2,0){$y$}
\rput(5.5,-1.25){$z^{-1}$}
\rput(3.65,-2){$\alpha$}
\rput(1.5,-2.5){$H$}
\rput(2.1,-0.5){$-$}
\rput(1.45,0.35){$+$}
\psframe(1,-3)(6.5,1)
\pspolygon(4,-1.5)(4,-2.5)(2.5,-2)
\psline{->}(0.25,0)(1.5,0)
\psline{->}(1.75,-2)(1.75,-0.25)
\psline{->}(5.5,-2)(4,-2)
\psline(2.5,-2)(1.75,-2)
\psline{->}(2,0)(7,0)
\psline(5.5,-1.7)(5.5,-2)
\psline{->}(5.5,0)(5.5,-0.75)
\psframe(5, -1.7)(6,-0.75)
\pscircle(1.75,0){0.25}
\psline(1.5,0)(2,0)
\psline(1.75,0.25)(1.75,-0.25)
\end{pspicture}
\end{verbatim}