im trying to get a volume in a containment pit.how do i set the bot. 4 corners to a 3d box to 4 separate elevations but keep the top 4 corners at a set elevation. or make a solid object at the different elevations to subtract from a d box

Create the top and bottom of the box out of 3DPolylines then use the LOFT command?  Just guessing as I am not on my CAD computer to test.Can you upload a drawing we can play with?I may have hit upon a solution that starts with the suggestion above but I can't explain it fully in words as it may seem too complicated.  However, give me access to a drawing and I might be able to provide you with something you can turn around and use. 
John Connor2016-09-26 20:20:16

I guess you found a solution on your own or you gave up.  Which is it?