Rock vs. knife? Seriously? You'll probably be stabbed or cut a few times before you land a solid bash with the rock. You have the "run away" part correct- if you're unarmed (or concealed carrying, holstered), do not engage. Get distance so you can draw your weapon or just run as fast as you can. **All it takes is ONE STAB OR CUT to the right part of your body, and you're fucking dead a few minutes later.** In a scenario where you cannot flee, and are unarmed, you should try to grab something BIGGER THAN THE KNIFE. A pipe, a broom handle, anything that can potentially keep the fucker out of stabbing distance. Using a rock as a bludgeon means you *must* get within "stab in the guts" range. Also most disarming techniques you'll see in shit like Krav Maga do not work on real, determined attackers- they only work on a student who is participating in the demonstration. Your best bet, unarmed and unable to flee or find a good improvised weapon, is to go "2 on 1"- both of your hands controlling the attacker's knife hand. The attacker (and you, probably) will have a sort of tunnel vision focus on the knife. So when a struggle begins over the knife, their focus will be entirely on retaining the knife- this is where headbutts and such come into play. Do you have any articles or videos of a knife attack being stopped by a guy bashing him on the head with a rock? I'm sure it has happened, but my point is that this shouldn't be your immediate option (which should be running away or shooting the bastard).