To Convert Contiguous Surfaces That Enclose a Volume to a 3D Solid Object
Click
Modify menu
Surface Editing
Sculpt
.
Select surfaces that enclose a watertight volume (that is, there must be no gaps between the surfaces).
A solid object is created.
Related Concepts
About Converting Surfaces and Meshes to 3D Solids
Related Tasks
To Convert Objects With Thickness to Extruded Solids
To Convert a Mesh Object to a 3D Solid