Barcelona boxing, kickboxing, muay thai self defence against the knife.
Boxing is an Olympic sport. Boxing the most perfect hand punching technique. Boxing is the most perfect technique of defence against punches with hands. Boxing prolongs life. Boxing makes a man cheerful and happy.
Knife is the oldest weapon. Originally, the knife was made of stone. As technology developed, the knife became bronze, then copper, metal. The knife is the most advanced edged weapon. The knife is the most dangerous cold weapon.

Can boxing be used as self-defence against a knife?
I’ve used it twice. I was lucky. I knocked out a knife-wielding attacker. That’s why I’m alive. I wouldn’t advise anyone to do it again. But my case is the exception to the rule. The statistics of knife use – lethal outcome.

To summarise the above.
Boxing cannot be used as self-defence against a knife.
Selling self-defence lessons against a knife is a crime. You can’t cheat if the payback for cheating is life.
Remember there is no self-defence against a knife with empty bare hands.
As self-defence against a knife is suitable spring from a tractor, a board from a bench, well or a gun if you can get it in time.
But since none of you usually does not go with a spring from the tractor or a board from the bench remains to avoid getting into situations where you will be attacked with a knife.
Take care of yourself and your loved ones. Avoid trainers who promise you invincibility.