\documentclass[12pt]{article}
%%% The diagonal line produced by the slashbox package
%%% is rather jagged and unwieldy.
%%% The diagbox package does a better job.
%%% Try loading only one of these packages to see
%%% the difference -- if diagbox is loaded at all,
%%% it overrides slashbox's behavior.
% \usepackage{diagbox}
\usepackage{slashbox}
\begin{document}
\title{Table cells with diagonal lines}
\author{(Uses sample text from \texttt{slashbox} package)}
\date{}
The usage is pretty straightforward, such as
\bigskip
\noindent
\begin{tabular}{|l||*{5}{c|}}\hline
\backslashbox{Room}{Date}
&\makebox[3em]{5/31}&\makebox[3em]{6/1}&\makebox[3em]{6/2}
&\makebox[3em]{6/3}&\makebox[3em]{6/4}\\\hline\hline
Meeting Room &&&&&\\\hline
Auditorium &&&&&\\\hline
Seminar Room &&&&&\\\hline
\end{tabular}
\bigskip
You may include a newline (\verb+\\+) in `Room' and/or `Date'.
Note that you will get spaces aside the slash line if there is a
wider column in the same column of a different line.
In such a case, you need to specify the width of the slashed column
by saying
\bigskip
\noindent
\begin{tabular}{|l||*{4}{c|}}\hline
\backslashbox[48mm]{Room}{Date}
&\makebox[3em]{5/31}&\makebox[3em]{6/1}&\makebox[3em]{6/2}
&\makebox[3em]{6/3}\\\hline\hline
Room With a Long Name &&&&\\\hline
Auditorium &&&&\\\hline
Seminar Room &&&&\\\hline
\end{tabular}
\bigskip
The specified width is neglected if it is narrower than the natural
width of the column.
\verb+\(back)slashbox+ assumes by default that there is a blank space
of width \verb+\tabcolsep+ on both sides of the column.
Thus the slash line might exceeds the boundary when you use \verb+@{}+
etc.
You can avoid it by specifying
\bigskip
\noindent
\begin{tabular}{|@{\ $\bullet$\hspace*{3mm}}l||*{5}{c|}}\hline
\multicolumn{1}{|@{}l||}{\backslashbox[0pt][l]{Room}{Date}}
&\makebox[3em]{5/31}&\makebox[4em]{6/1}&\makebox[3em]{6/2}
&\makebox[3em]{6/3}&\makebox[3em]{6/4}\\\hline\hline
Meeting Room &&&&&\\\hline
Auditorium &&&&&\\\hline
Seminar Room &&&&&\\\hline
\end{tabular}
\bigskip
Here \verb+[l]+ tells the command that there is no extra space on the
left of this column. You can use \verb+[r]+ and \verb+[lr]+ likewise.
You have to also specify the width of the column in this case, but it
can be 0pt.
\end{document}
