A headgear is an appliance used to create external pressure to guide the growth of the face, jaws, and teeth. Facebow and Hook are the two commonly used headgear types. These differ in the method of attachment and the direction and amount of pressure that you can apply. 

The headgear type and the length of time for which it needs to be worn will depend upon the severity of the orthodontic defect and the type of jaw growth that needs to be corrected. Always wear the headgear as instructed and wear it for the prescribed length of time each day.