Blender Modifiers
From Wikicliki
boolean
Blender: Why won't Boolean modifier work?
- Check that items do not have a negative scale in any axis
- Check that normals are not flipped. Select all, Ctrl-N
- Add more loop cuts so tris will be containers and not mess up topology.
- Check for non-manifold Shift-Ctrl-Alt-M
- are objects duplicates? u> object data to make object a new separate datablock