Avoid engaging a lethal weapon. Flee if possible. Engagement means grievous or fatal injury. Should you find yourself facing a lethal weapon then keep in mind that once your opponent is disarmed, you will commit a criminal offense if you turn that weapon on an unarmed attacker. You could go to prison for using the same weapon the attacker used on you. This said, should you find yourself facing a knife and you can't flee, then watch Julio Anta of Anta's Fitness and Self Defense School teach his students what to do. Recorded live in a class setting.