Used to delete the blocks from the topology.
If Delete permanently is toggled OFF, the block will be moved to the VORFN part. The VORFN part is essentially dormant and mesh is not computed for it, however it does help to maintain connectivity. Blocks can be retrieved from the VORFN region with Add Blocks to Part.
If Delete permanently is toggled ON, it will permanently delete the block. At this point connectivity will be broken and the VORFN region will be rebuilt. This can be useful in some situations, but this will also result in a re-indexing of the blocking. The resulting index structure is usually more complicated and may be more difficult to work with.