I've heard how knife hits get you fucked up with less amount of bud, but is it really worth the effort?
They fuck you up because the smoke is very hot and harsh and you're getting it all at once and because of all the metal fumes you are inhaling lol
You could buy glass blades I seen them at my lhs. And honestly I do blades when I have barely any weed. It gets you fried, and it's really conservative.