Jalandhara bandha or Chin Lock is a physical and energetic way to activate and and contain the muscular actions of your upper body. Try Chin Lock as a way to keep your spine straight and your neck free from compression. It's also a nice way to keep the head/neck/spine in alignment in lateral postures such as in triangle (trikonasana) to half moon (arhda chandrasana). A great healthful action for those of you with neck and shoulder sensitivity.