the 21-foot rule means you are putting your life in danger if the knives are allowed closer, I prefer holding a social worker in front of me.
I know what it means and because of the internet it gets posted all the time.
If a bad guy and I get to choose from the knife on the table or the gun on the table, and I get to choose first, then I pick up the gun, if I am to fight unarmed, then I prefer he have a knife instead of a gun, if he is five feet away, then I prefer that he have a knife instead of a gun.
Knives are inferior to guns, if you have to take up mugging unarmed Hell’s Angels walking alone through the alleys, for grocery money, and you get a choice of weapons for your new trade, which do you choose?