"The Solidify modifier takes the surface of any mesh and adds depth, thickness to it." Use this tag for any questions about the use of the solidify modifier.
The blender manual entry for the Solidify Modifier says
The Solidify modifier takes the surface of any mesh and adds depth, thickness to it.
The modify is often used to add thicknesses to meshes that represent things like windows, cups, and walls; but can add thickness to any mesh.
Use this tag for any questions about the use of the solidify modifier.