\usepackage{multirow} % preamble \usepackage{slashbox} % preamble \begin{tabular}{|l|l|l|l|}\hline \multirow{2}{1.3cm}{\backslashbox{a}{a}} & b & c & d\\\cline{2-4} & e & f & g \\\hline h & i & j & k\\\hline l & m & n & o\\\hline \end{tabular}