The code below will produce a MTMM matrix for three traits and three methods. Reliabilities appear in (parentheses), concurrent validity coefficients appear in bold font, discriminant validity coefficients appear in regular font. Just replace Trait A-C with your traits, Methods 1-3 with your methods, and all xx with you coefficients.
\begin{center}
\begin{tabular}{l l c c c c c c c c c c c}
\hline
&&\multicolumn{3}{c}{Method 1}&&\multicolumn{3}{c}{Method 2}&&\multicolumn{3}{c}{Method 3} \\
&&Trait A&B&C&&A&B&C&&A&B&C\\ \hline
1.&Method 1\\
&A. Trait A&(.xx)\\
&B. Trait B&.xx&(.xx)\\
&C. Trait C&.xx&.xx&(.xx)\\
\\
2.&Method 2\\
&A. Trait A&\textbf{.xx}&.xx&.xx&&(.xx)\\
&B. Trait B&.xx&\textbf{.xx}&.xx&&.xx&(.xx)\\
&C. Trait C&.xx&.xx&\textbf{.xx}&&.xx&.xx&(.xx)\\
\\
3.&Method 3\\
&A. Trait A&\textbf{.xx}&.xx&.xx&&\textbf{.xx}&.xx&.xx&&(.xx)\\
&B. Trait B&.xx&\textbf{.xx}&.xx&&.xx&\textbf{.xx}&.xx&&.xx&(.xx)\\
&C. Trait C&.xx&.xx&\textbf{.xx}&&.xx&.xx&\textbf{.xx}&&.xx&.xx&(.xx)\\
\hline
\end{tabular}
\end{center}