Converts a shell object back to normal surfaces.
Access this tool from the Surface Edit tool palette:

Shell Unstitch Options
Keep the original shell after it is unstitched into surfaces.
Shell Unstitch workflow
You can use the Align tool to make the surface edges match exactly.
You can change the tolerance governing how close surface edges must be. In the option box, turn off Use construction options and set the Tolerance value.
If you stitch an object, then scale it, then unstitch it, you may not be able to re-stitch the object. This is because the scaling operation can increase the gaps between surfaces beyond the current tolerances.