if you do it right., knife hits putt off thick dark yellowish smoke.....like a severely milked bong, and it fucks you up. gravity bongs you just cut the bottom of some kind of container, like milk craton or coke 2 liter and make a screw on bowl out of the cap. you put it in a tank of water(anything the bong can fit in all the way down) and put weed in the bowl. you light the top of the bowl and start slowly pulling it out of the water, and it naturally pulls smoke into the chamber, when your about to pull it out of the water, unscrew the cap, put your mouth over it, and push it down into the water, and let the nice, warm smoke smash into your lungs. try not to swallow the water (if you push down too fast). magnifying glass hits, you just light any bowl with the sun and a magnifying glass, burns really slow, and gives off very potent hits.....i think its bc it burns at a lower temp, but im not sure.