This is probably best explained with an example. I have the following table, where the \"A\" cell spans two rows, and the \"B\" cell spans two columns.
\\begin{t
\multirow{2}{*}{\hfil A}
\hfil will automatically calculate the width of the cell and insert a half-width space
\hfil
To insert a full cell-width space, which will right-justify a single cell, use \hfill. There are also \vfil and \vfill analogues.
\hfill
\vfil
\vfill