I have many thousands of multipatches, closed and open, that need to be 'merged' based on an attribute. The only way open to me is selecting and merging manually with edit tools. All the geoprocessing tools I can find are too restrictive. I do not need to worry about the multipatches becoming 'open' (internal walls). Hence a tool that can make multipart mutipatches based on an attribute would suit me perfectly and save months of work.