Per U.S. Air Force Manual 34-515, USAF Honor Guard, the chrome hat buttons on the Honor Guard hat are also screws that can be loosened in order to properly position the chinstrap, then tightened to secure the chinstrap in place.
Chrome hat buttons for Enlisted Honor Guard personnel feature the “wing and star” insignia, today called the “Hap Arnold device” or “Hap Arnold star” and originally used as the symbol for the United States Army Air Corps. When tightening the screw-in buttons, be sure that you screw them in enough to secure the straps while making sure that the wings in the design are pointing skyward. As with all chrome devices worn on the Honor Guard uniform, the chrome hat buttons should be highly polished at all times.
According to the 2009 monograph titled “Of Uniform Concern: A Casual History of the US Air Force Service Dress Uniform” by Kalikiano Kalei, the Hap Arnold device was first introduced into Air Force uniform design on the buttons of the Service Dress Uniform authorized by Air Force Chief of Staff General Merrill McPeak in 1991.