The level at which the vertebral artery enters the transverse foramen of the 6th cervical vertebra The site at which the carotid artery can be pressed against the carotid tubercle of the oth cervical vertebra•The level at which the vertebral artery enters the transverse foramen of the 6th cervical vertebra. •The site at which the carotid artery can be pressed against the carotid tubercle of the 6th cervical vertebra