Hi Kixum. All the groups are different heights (it's a city. Each city block is a group. Some blocks have taller building than others). How can I align them all to the same elevation? Where is the align tool? Mark, I am trying to "land" them all on a plane, but maybe I will switch to a wide flat cube and try again...? I didn't notice any hitch, but C4 is starting to be less than responsive with so much geometry.... If I open the group and set the flat bases to "collide", then close the group to move it all at once.... Is that what I'm supposed to do? Never used collision detection and as yet to figure out how to make it work.