SketchUp's Solid tools work only on SketchUp solids. In SketchUp, a solid is any 3d model (component or group) that has a finite closed volume. A SketchUp solid cannot have any leaks (missing faces or faces that do not meet at an edge).
You can select a component or group and visit the Entity Info dialog box to see if the selection is a solid. If there is a volume listed, the selection is a SketchUp solid. If there is no volume listed, the selection is not a solid and likely has a leak.
The following image contains several solids:
There are six Solid tools in SketchUp - all operate only on solid models:
- The Intersect tool () operates on two or more solids and results in only the overlapping parts.
- The Subtraction tool () operates on two solids and merges the intersecting geometry from the second selected solid with the first selected solid. The first solid is then removed leaving only the second solid (minus its intersecting geometry).
- Just like the Subtraction tool, The Trim tool () operates only on two solids and merges the intersecting geometry from the second selected solid with the first selected solid. Unlike the Subtraction tool, the Trim tool leaves the first solid in the result.
- The Split tool () splits all of the parts of two solids into separate groups or components wherever the solids overlap.
- The Union tool () merges all outer faces of two or more overlapping solids to create one larger SketchUp solid. The Union tool leaves all internal geometry in the result.
- The Outer Shell tool () works just like the Union tool, but removes all internal geometry from the result. Therefor, the Outer Shell tool is the preferred tool for creating lightweight models, such as buildings for Google Earth, because only the outer faces of the model are needed to convey the design.