Often, copyright assignments are used when the rights to a work are given, so the party that obtains the rights can use that work for any desired purpose. Assignments of copyright allow the simple transmission of works protected by copyright. They contain all the information necessary to register the assignment with the United States Copyright Office if either party so wishes. However, registration with the U.S. Copyright Office is not absolutely necessary, although it is a good way to ensure that everything goes smoothly with the transfer of copyright. Copyright transfers relate to U.S. copyright law, which is covered by a federal law called the Copyright Act of 1976. This document allows the parties to fill in the details of the work to be transferred or the works to be transferred and to ensure that everything necessary for registration in the U.S.