Is there a node suffix for the corners of a node?
I'd like the brace in this example to go from the lower-left corner of the first box to the lower-right corner of the last.
\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes,patterns,decorations.pathreplacing}
\begin{document}
\tikzstyle{frame} = [rectangle, draw, fill=blue!20,
text width=4em, text centered, minimum height=3em, node distance=3cm]
\begin{tikzpicture}
\node [frame] (f1) {$f_1$};
\node [frame, right of=f1] (f2) {$f_2$};
\node [frame, right of=f2] (f3) {$f_3$};
\draw [decoration={brace,mirror},decorate] (f1.center) -- (f3.center);
\end{tikzpicture}
\end{document}
south west
is the lower left.