A chair's design may be protected by a design patent (and perhaps by trademark or copyright) however, the patent will not prevent others from marketing the functional equivalent, i.e. a chair of a different design. Design patents are less expensive to obtain, the application principally relying upon the drawings to set out the design sought to be protected, and less expensive to maintain. A design patent is valid for a period of 14 years from date of issue and requires no maintenance fees during its lifetime, unlike a utility patent.

Whether another design infringes a patent design involves a two-part test. First, the court considers whether, in the eyes of an ordinary observer, the designs are substantially the same. Second, the court questions whether the "infringing" design appropriates the novel features of the patented design. The patented design is considered in its entirety, including all ornamental features included in the patent drawings.

Distinctive designs may distinguish product lines from the competition like trademarks. This distinctiveness is not the purpose of a design patent and is not protected by the patent. Instead, the design patent protects the ornamental consumer appeal of the product design. Accordingly, while ornamental features which are concealed or obscure during "normal use" are not protected by a design patent, the very purpose of appealing to consumer interests means that "normal use" may extend from the product's manufacture to destruction. For this reason, even a product that may be concealed upon installation by the consumer may qualify for a design patent where the design is intended to ornamentally appeal to the consumer and encourage purchase.

The overlapping nature of various intellectual property rights deserves particular attention whenever considering a design patent on an article of manufacture. As previously mentioned, the ornamental design of the article may provoke trademark, trade dress or copyright issues, either at the time of the invention or at later dates. While the patent will not protect these other rights, steps can, and should, be taken to separately protect all available intellectual property rights. This can be important where, for instance, the product line will have a lifetime exceeding the 14 year life of the patent. For these reasons, it is important to consider ALL the possibilities and revisit those issues on a recurring basis. Today's design may be tomorrow's trademark.