Letters patent (always in the plural) are a type of legal instrument in the form of a published written order issued by a monarch, or government. They are generally used in granting an office, right, monopoly, title, or status to a person or corporation. Letters patent can be used for the creation of corporations or government offices. They may be used for the granting of city status or a coat of arms. Letters patent are issued for the appointment of representatives of the Crown, such as Governors and Governors-General of Commonwealth realms. In the United Kingdom they are also issued for the creation of peers of the realm. A particular form of letters patent has evolved into the modern patent (referred to as a utility patent or design patent in United States patent law). This grants exclusive rights of an invention (or a design in the case of a design patent). In this case it is essential that the written grant should be in the form of a public document so other inventors can consult it to avoid infringement. It is also important to understand how to "practice" the invention or put it into practical use.