\documentclass{article}

\usepackage{array}% To join corners of bordered arrays

\begin{document}

\begin{tabular}{ | l | l | }
  \multicolumn{1}{c}{} & \multicolumn{1}{c}{heading} \\
  \hline
  A & \\
  \hline
  B & \\
  \hline
\end{tabular}

\begin{tabular}{|l|@{\hspace{2em}}|}
  \hline
  A \\
  \hline
  B \\
  \hline
\end{tabular}

\end{document}