The depth of insertion is 0.5 - 1 cun. Deep needling is avoided lest the spinal cord be impaired. The angle of insertion depends upon the angle of the spinous process. The spinous processes of the thoracic vertebrae are down-bearing, so the acupoints below them should be needled obliquely upward; while the spinous processes of the lumbar vertebrae protrude almost posteriorly and horizontally, so the acupeints below them can be needled perpendicularly; the acupoints on the caudal-sacral region are needled obliquely upward.
Dazhui (GV 14): It is needled perpendicularly or obliquely 0.5 - 1 cun. The needle is inserted slowly to a proper depth. Deep insertion should be avoided lest the vertebral canal be punctured and the spinal cord is impaired.
Changqiang (GV 1): The needle should be parallel to the coccyx and inserted between the rectum and coccyx. Otherwise the rectum may be impaired.