Design patents are intended to protect the ornamental and cosmetic aspects of products but not their function. The disclosure and description of the invention in a design application is entirely in the drawing and not in the words. When a unique appearance is important to a product's success, a design patent can be a worthwhile investment. Computer icons, which are substantially all appearance and no substance, can be protected with design patents. On the other hand, internal and normally unseen components of a machine can not be protected with a design patent, regardless of how unusual their appearance may be.
Timing is often important in design filings.
Filing before then invites problems when subtle appearance changes occur as the product is being tooled up for manufacture. There is little breadth of protection provided by design patent coverage. Because a design patent can be obtained for a somewhat unusual looking version of a well-known product, several operators of invention marketing scams regularly steer people into getting worthless design patent protection. To compare design patents with other froms of intellectual property, see the linked table .