When skirting is first primed, it may lift the surface of the wooden or MDF material somewhat, which must then be sanded off before a second coat is applied to become smooth. All of this is to be done before a final coat is applied by you or your carpenter/decorator, on site. We usually refer to this preparatory process as "double primed and sanded". Many manufacturers will skip or shortcut this process, resulting in very rough boards out of the factory. Please bear in mind that even double primed and sanded does not guarantee a smooth finish and some sanding may be required before a final coat is applied.