Cut form geometry with a solid form. 
 When you use a solid to cut geometry, the overlapping area is removed and the abutting solids remain. Solid forms will only cut the following solids: 
- Form elements 
  
- Forms with divided surfaces 
  
- Forms with geometric combinations 
  
- Family instances inside of the massing editor. 
  
- Create two adjacent solid forms. 
- Click Modify tab Geometry panel Geometry panel  (Cut). (Cut).
- Select the solid form to be cut. 
- Select the cutting solid form. 
  The solids cut accordingly. The 2 forms can be edited and maintain the cut relationship. 
   Note: When a solid cut geometry mass is imported into a project, you cannot interact with the individual solids. Similarly, if the solid cut geometry had levels applied to it, they will not be recognized in the project environment.