Your comment is rather ambiguous. The upper region of the trapezius assists in retraction (adduction) of the scapulae and also in elevation of the shoulder girdle. The rhomboids, along with the middle trapezius, are prime movers for shoulder girdle adduction. One cannot strengthen the rhomboids without also strengthening the middle traps. I suspect that the best answers to your query is to help improve posture and to somewhat reduce the risk of cervical and upper thoracic postural problems.