Drawing lines in tables?

Question

I use the following code to draw a table:

\makebox[\textwidth]{%
\begin{tabularx}{\textwidth}{|X|S|S|S|S|S|X|}
  \hline
  & $--$ & $-$ & $-/+$ & $+$ & $++$ &\\
  \hline
  The necessary information was easy to find & $\square$ & $\square$ & $\square$ & $\square$ & $\square$ & The necessary information was hard to find\\
  \hline
  Information retrieval requires redundant user input  & $\square$ & $\square$ & $\square$ & $\square$ & $\square$ & Information retrieval does not require redundant user input\\
\\\hline
\end{tabularx}%
}

Now the table looks like this:

If I dont use the last \\\hline:

\makebox[\textwidth]{%
\begin{tabularx}{\textwidth}{|X|S|S|S|S|S|X|}
  \hline
  & $--$ & $-$ & $-/+$ & $+$ & $++$ &\\
  \hline
  The necessary information was easy to find & $\square$ & $\square$ & $\square$ & $\square$ & $\square$ & The necessary information was hard to find\\
  \hline
  Information retrieval requires redundant user input  & $\square$ & $\square$ & $\square$ & $\square$ & $\square$ & Information retrieval does not require redundant user input\\
\end{tabularx}%
}

It looks like this:

So how can I make the last line correctly?

Answer 1

You have two \\ now:

... redundant user input\\
\\\hline
\end{tabularx}%

Before you had no \\:

... redundant user input
\hline
\end{tabularx}%

which causes the mentioned error.

You need only one \\:

... redundant user input\\
\hline
\end{tabularx}%

And then it works properly.

The reason why some lines are missing when you have two \\ is that the cells are not filled out, e.g. there are not & in the last row. The lines are only drawn with the cells. Therefore no cells -> no lines.