I don't think I needed one ever. From reading early on, I stretched my jaw as much as I could all the time as soon as I could, I just ignored the pain as much as I could. I think I just do it all the time now without thinking about it. My wife asks if I'm tired, cause she thinks I'm yawning. Now that I think about it I do remember using my fingers as a gauge of how far I could open my mouth. At first I could barely get 2 fingers in vertically. I just checked & I can get 4 in vertically, now. I can't remember what the reference was about getting the jaw open early on & so I just worked on it from early on. Stretch, stretch, stretch! Jaw, neck, shoulder! Just do it!