In Chapter One, Jani introduces us to the nuances of the ha and tha engagement of Jalandhara Bandha, or chin lock. Chapter Two looks at the supporting tongue bandha known as Jihva Bandha.
So good to remember that it's not about the form or shape or how it looks. It's about inner work. Awareness of the inner structure and the space moving around it on which you build a healthy body. Very nice detail.