For my thesis, I often need to write blocks attached to each other. More explicitely, I want to have blocks as in page 13 of <http://eprint.iacr.org/2006/392.pdf>.

**EDIT**: @morbusg. Is it possible to (easily?) fix the following (in order to get what we want)

```
 \begin{figure}
 \centerline{\vbox{%
   \offinterlineskip % no lead between lines
   \dimen0=4.5em % size of a square cell
   \mathsurround0pt % precaution; although I've newer seen it used
   \def\cr{\crcr\noalign{\hrule}} % put a rule between every row with \cr
   \halign{&\vrule\hbox to\dimen0{$\vcenter to\dimen0{}\hfil\scriptstyle#\hfil$}\crcr
     \omit& \omit& \multispan3\hrulefill\crcr\noalign{\kern-.4pt}
     % ^omit drawing a box for the first two columns, then, span the next
     % three columns drawing the "hat", and finally, back up the amount of
     % the width of the rule so that the vertical and horizontal rules
     % fit together.
     \omit& \omit&\omit & W(-k-1,1) & W(-k,1) & W(-k+1,1) &\omit\vrule \cr
     W(-k-4,0) & W(-k-3,0) & W(-k-2,0) & W(-k-1,0) & W(-k,0) & W(-k+1,0) & W(-k+2,0) & W(-k+3,0)&\omit\vrule \cr
     }
 }}
 \caption{}
 \end{figure}

```

And also

```
\begin{figure}[H]

\centerline{\vbox{%
  \offinterlineskip % no lead between lines
  \dimen0=5em % size of a square cell
  \mathsurround0pt % precaution; although I've newer seen it used
  \def\cr{\crcr\noalign{\hrule}} % put a rule between every row with \cr
  \halign{&\vrule\hbox to\dimen0{$\vcenter to\dimen0{}\hfil\scriptstyle#\hfil$}\crcr
    \omit& \omit& \multispan3\hrulefill\crcr\noalign{\kern-.4pt}
    % ^omit drawing a box for the first two columns, then, span the next
    % three columns drawing the "hat", and finally, back up the amount of
    % the width of the rule so that the vertical and horizontal rules
    % fit together.
    \omit        & W(k-1,2n+2)   & W(k,2n+2) & W(k+1,2n+2) & ? &\omit\vrule \cr
    ? & W(k-1,2n+1) & W(k,2n+1) & W(k+1,2n+1)   & ? &\omit\vrule \cr
    ? & W(k-1,2n)   & W(k,2n)   & W(k+1,2n)   & ?  &\omit\vrule \cr
    ? & W(k-1,2n-1) & W(k,2n-1) & W(k+1,2n-1)   & ? &\omit\vrule \cr
    }
}}
\label{Sdouble}
\end{figure}

```