the unwritten rule of senatorial courtesy applies to what appointments
Senatorial courtesy Senatorial courtesy is a long-standing unwritten, unofficial, and nonbinding political custom (or constitutional convention) in the United States describing the tendency of U.S. senators to support a Senate colleague in opposing the appointment to federal office of a presidential nominee from that Senator's state.[1] The practice is motivated by a general sense of collegiality among Senators and the assumption that a Senate colleague will have the best first-hand knowledge of the personal character and qualifications of nominees from his or her own state. It is also viewed as an "important source of political patronage"[2] for U.S. senators.
Appointments Clause The Appointments Clause is part of Article II, Section 2, Clause 2 of the United States Constitution, which empowers the President of the United States to nominate, and with the advice and consent (confirmation) of the United States Senate, appoint public officials. Although the Senate must confirm certain "principal" officers (including ambassadors, Cabinet secretaries, federal judges, and United States Attorneys), Congress may by law delegate the Senate's advice and consent role when it comes to "inferior" officers (to the President alone, or the courts of law, or the heads of departments).