I want to add a diagonal line in a the top line of a table where the other entries on the first row are written sideways. I've tried \backslashbox and \diagbox and \diag but no matter how I change the values the topmost position of the line does not increase without lifting all the other entries.
\usepackage{slashbox}
\begin{table}[ht]
\centering
\caption{Pugh matrix}
\begin{tabular}{|l|c|c|c|}
\hline\hline
\backslashbox[130pt]{Property}{Concept} & \begin{sideways} Concept 1 \end{sideways} & \begin{sideways} Next concept \end{sideways} &
\begin{sideways} Next concept/increase line{\ } \end{sideways} \\
\hline
Do this & 0 & 0 & - \\
Do that & 0 & 0 & 0 \\
Do it quickly & 0 & + & + \\
Do the task quickly & 0 & 0 & - \\
\hline
SUM: & 0 & +1 & +2 \\
\hline
Ranking & 2 & 2 & 1 \\
\hline
Keep & NO & NO & YES \\
\hline\hline
\end{tabular}
\label{tab:Pugh_matrix2}
\end{table}