Please post this kind of specific question in a relevant thread. The CutNfill thread already contains several posts about why two seemingly solid objects subtract to give a non-solid, which in turn reports 0 volume. This is not a limitation of the tool itself, but one of SketchUp's built-in methods to manipulate solids. If the subtractions leave tiny edges SketchUp faces to form the related faces in the results, and non-solids can't have a volume ! See some of related posts here... http://sketchucation.com/forums/viewtopic.php?p=641870#p641870 http://sketchucation.com/forums/viewtopic.php?p=651884#p651884