This common problem is worst with small bougies, such as in this paediatric example of a child with severe burns and a difficult airway.  The bevel of the ETT allows the tip of the tube to stick out right (laterally) of the bougie and snag on the right arytenoid cartilage.  This can be remedied by withdrawing the ETT slightly (to disengage it from the arytenoid), effecting a one-quarter counter-clockwise rotation of the ETT on the bougie (bringing the bevel and tip of the ETT into a superior midline position snug with the bougie), and then advancing again.