“below of=” ? more than one block?

Question

I want to make a block c under two blocks a & b. So far I'm able to do it for only one block

\node [block, below of=a]    (c)    {filter};

Answer 1

Please always post complete code starting from \documentclass{..} and ending at \end{document}. I don't know how block is defined.

Your question is not clear. Whether a ,b and c are one below the other or a and b side by side with c below them at the center?

Please note that below of=a is deprecated. you should use below = of a instead with \usetikzlibrary{positioning}. Here are the possibilities.

\documentclass[tikz]{standalone}
\usetikzlibrary{positioning}
\begin{document}
    \begin{tikzpicture}
      \node (a) {Coffee};
      \node [below = of a] (b) {Sugar};
      \node [below = of b] (c) {Filter};    
    \begin{scope}[xshift=8cm]
      \node (a) {Coffee};
      \node [below left = of a] (c) {Filter};
      \node [above left =  of c] (b) {Sugar};
    \end{scope}  
    \end{tikzpicture}
\end{document}

You can control the distances manually like below left = 1cm and 2cm of a. For details refer pgfmanual.