Distance indicators on a lateral cervical X‐ray film in the neutral position. X1, distance between the temporomandibular joint and tip of the upper incisors; X2, perpendicular distance from the hard palate to the tip of the upper incisors; X3, length of the mandibular body; X4, vertical distance from the highest point of the hyoid bone to the mandibular body; X5, distance from the antero‐inferior border of the fourth cervical vertebra to the antero‐superior border of the first cervical vertebra; X6, atlanto‐occipital gap; X7, horizontal distance from the highest point of the hyoid bone to the border of the nearest cervical vertebra; X8, distance between the spinous processes of first cervical vertebra and the second cervical vertebra.