OVERFLOW export supports 3D structured grids only. Fidelity Pointwise writes only OVERFLOW's BCINP namelist.
Note that while Fidelity Pointwise can create overlapping grids as required for OVERFLOW, the hole cutting and other overlap calculations must be computed using some other software such as PEGASUS, OVERFLOW's preprocessor. In fact, the grid exported for OVERFLOW is actually formatted for PEGASUS. The PEGASUS grid file is Fortran unformatted, and you are given a choice of Single or Double precision. This grid file also contains the block names.