\centering\begin{tikzpicture}[x=12pt,y=12pt]
{
\draw[pattern=north east lines, pattern color=gray] (0,6) rectangle (4,2);
\draw[fill=gray] (3,2) rectangle +(1,1);
\draw[step=1] (0,0) grid (6,6);
}
\end{tikzpicture}