The approximate position of the oblique fissure on a patient, in quiet respiration, can be marked by a curved line on the thoracic wall that begins roughly at the spinous process of the vertebra TIV level of the spine, crosses the fifth interspace laterally, and then follows the contour of rib VI anteriorly (see pp. 241–242).
The horizontal fissure follows the fourth intercostal space from the sternum until it meets the oblique fissure as it crosses rib V.