A useful technique for modeling a complex 3D curved solid is to first create a surface
and then convert it to a 3D solid by thickening it. If you select a mesh face to thicken,
you can choose to convert the mesh object to a solid or surface before completing
the operation.

List of Options

The following prompts are displayed.

Surfaces to thicken

Specifies one or more surfaces to thicken into solids.

Thickness

Sets the height of the thickened object.