This document discusses different approaches to combined activator and headgear orthopedics. It describes the biomechanics of headgear and how forces applied in different locations can result in different rotations and movements of the maxilla. Several appliance designs are summarized, including those developed by Stocklie and Teuscher, Pfeiffer and Grobety, and Hickham. The Stocklie and Teuscher design uses an activator, transpalatal bar, and headgear to hold the maxilla vertically and sagitally while positioning the mandible forward. Pfeiffer and Grobety advocated using an activator along with cervical extraoral force to correct Class II malocclusions.