We usually think of the process for appointing a federal judge as: nomination, Senate Judiciary Committee hearing, Senate confirmation vote, and swearing-in. This report from the Congressional Record Service [link] explains the process that takes place between the confirmation by the Senate and the actual swearing-in:
After Senate Confirmation
Under the Constitution, the Senate alone votes on whether to confirm presidential nominations, the House of Representatives having no formal involvement in the confirmation process. If the Senate votes to confirm the nomination, the secretary of the Senate then attests to a resolution of confirmation and transmits it to the White House.154 In turn, the President signs a document, called a commission, officially appointing the individual to the Court. Then, the following technical steps occur:
The signed commission is returned to the Justice Department for engraving the date of appointment . . . and for the signature of the attorney general and the placing of the Justice Department seal. The deputy attorney general then sends the commission by registered mail to the appointee, along with the oath of office
and a photocopy of the confirmation document from the Senate.155
Upon the appointee’s receipt of the commission and accompanying documents, only the formality of being sworn into office remains. In fact, however, the incoming Justice takes two oaths of office — a judicial oath, as required by the Judiciary Act of 1789, and a constitutional oath, which, as required by Article VI of the U.S. Constitution, is administered to Members of Congress and all executive and judicial officers. In recent years, the usual practice of new appointees has been to take their judicial oath in private within the Court, and, as desired by the Presidents who nominated them, to take their constitutional oaths in nationally televised ceremonies at the White House.156