We present a technique for matching adjacent treatment fields over the spine. Our approach relies on identifying vertebral bodies and correlating their position to the table top markings present on the simulator table. The vertebral body levels are verified with films taken with the isocenter at the borders (nondivergent border films) so the "true" borders are identified. This is in contrast to using the usual divergent films, which may misrepresent the field borders with respect to the vertebral body level. An additional space between fields may be added as a precaution against overlap.