Design patents are available to any person who has invented any new and nonobvious ornamental design for an "article of manufacture." A design patent protects only the appearance of an article, not its structural or functional features. Design patents are prosecuted in essentially the same way as utility patents. A design patent has a term of 14 years from grant, and no fees are necessary to maintain a design patent in force. The drawing of the design patent conforms to the same rules as other drawings, but no reference characters are allowed and the drawing should clearly depict the appearance, since the drawing defines the scope of patent protection. The specification of a design application is short and ordinarily follows a set form. Only one claim is permitted, following a set form that refers to the drawing(s).