# How to do a table with top corner removed

I want to do a table with some columns (9) but I want the first 2 columns on the first row to be empty. I can't seem to be able to close the top of my table the way I do it.

\begin{tabular}{|c|c||c|c|c||c|c|c||c|}
\multicolumn{2}{c||}{}&\multicolumn{3}{c||}{Dimensions finies}&\multicolumn{3}{|c||}{   Dimensions brutes}\\
\hline
Identification & Qté & Long.&Larg.& Épais.& Long.& Larg.& Épais. &PMP\\
\hline
Dessus & $1$ & $46$ & $28$ & $6/4$& & & & \\
\hline
Pattes & $4$ & $37\sfrac{1}{2}$ & $3$ & $2$& & & & \\
\hline
\end{tabular}

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You can use \cline{i-j} to draw a line from column i to column j; however, I would like to suggest you the booktabs package to design your tables; your table with and without booktabs:

\documentclass{article}
\usepackage{booktabs}
\usepackage{array}

\begin{document}

\noindent\begin{tabular}{*{9}{|c}|}
\cline{3-8}
\multicolumn{2}{c}{}&\multicolumn{3}{||c||}{Dimensions finies}&\multicolumn{3}{|c||}{   Dimensions brutes}\\
\hline
Identification & Qté & Long.&Larg.& Épais.& Long.& Larg.& Épais. &PMP\\
\hline
Dessus & $1$ & $46$ & $28$ & $6/4$& & & & \\
\hline
Pattes & $4$ & $37\frac{1}{2}$ & $3$ & $2$& & & & \\
\hline
\end{tabular}

\vspace{20pt}

\noindent\begin{tabular}{@{}c*{7}{c}c@{}}
\toprule
& &\multicolumn{3}{c}{Dimensions finies}&\multicolumn{3}{c}{Dimensions brutes}\\
\cmidrule(r){1-2}\cmidrule(lr){3-5}\cmidrule(lr){6-8}\cmidrule(l){9-9}
Identification & Qté & Long.&Larg.& Épais.& Long.& Larg.& Épais. &PMP\\
\cmidrule(r){1-1}\cmidrule(lr){2-2}\cmidrule(lr){3-3}
\cmidrule(lr){4-4}\cmidrule(lr){5-5}\cmidrule(lr){6-6}
\cmidrule(lr){7-7}\cmidrule(lr){8-8}\cmidrule(l){9-9}
Dessus & $1$ & $46$ & $28$ & $6/4$& & & & \\
\midrule
Pattes & $4$ & $37\frac{1}{2}$ & $3$ & $2$& & & & \\
\bottomrule
\end{tabular}

\end{document}


As you can see, there's really no need for the vertical rules and the table now looks much better than before.

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Thanks, I'll look up the booktabs package. Any way to lengthen a bit the \cline, as you see there is space on the left side? –  Jean-Sébastien Aug 16 '12 at 23:56
@Jean-Sébastien I've updated my answer. –  Gonzalo Medina Aug 17 '12 at 0:33

For completeness, here's how to adequately align the vertical and horizontal rules in your code snippet:

\documentclass[twocolumn]{article}
\usepackage{xfrac}% http://ctan.org/pkg/xfrac
\usepackage[utf8]{inputenc}% http://ctan.org/pkg/inputenc
\begin{document}
\begin{tabular}{|c|cc|c|c||c|c|c||c|}
\cline{3-8}
\multicolumn{2}{c}{} & \multicolumn{3}{||c||}{Dimensions finies} & \multicolumn{3}{c||}{Dimensions brutes} \\
\hline
Identification & Qté & \multicolumn{1}{||c|}{Long.} & Larg. & Épais. & Long.& Larg.& Épais. & PMP \\
\hline
Dessus & $1$ & \multicolumn{1}{||c|}{$46$} & $28$ & $6/4$& & & & \\
\hline
Pattes & $4$ & \multicolumn{1}{||c|}{$37\sfrac{1}{2}$} & $3$ & $2$& & & & \\
\hline
\end{tabular}
\end{document}


The double vertical rule was added to the beginning of the third column rather than a shared vertical between the second and third.

Alternatively, consider this representation that uses a 1pt vertical rule (as opposed to two .4pt vertical rules with some gap):

\documentclass[twocolumn]{article}
\usepackage{xfrac}% http://ctan.org/pkg/xfrac
\usepackage{array}% http://ctan.org/pkg/array
\usepackage[utf8]{inputenc}% http://ctan.org/pkg/inputenc
\begin{document}
\begin{tabular}{|c|c!{\vrule width 1pt}c|c|c!{\vrule width 1pt}c|c|c!{\vrule width 1pt}c|}
\cline{3-8}
\multicolumn{2}{c!{\vrule width 1pt}}{} &
\multicolumn{3}{c!{\vrule width 1pt}}{Dimensions finies} &
\multicolumn{3}{c!{\vrule width 1pt}}{Dimensions brutes} \\
\hline
Identification & Qté & Long. & Larg. & Épais. & Long.& Larg.& Épais. & PMP \\
\hline
Dessus & $1$ & $46$ & $28$ & $6/4$& & & & \\
\hline
Pattes & $4$ & $37\sfrac{1}{2}$ & $3$ & $2$& & & & \\
\hline
\end{tabular}
\end{document}

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