This is instructions on how to make a gravity bong. Supplies needed ******Improvise and be creative! 1. A screen - can be purchased from headshops, or bought in hardware stores, even from a household sink. (just unscrew were the water comes out and theres a screen if you look you can see it.) 2. an apple 3. knife 4. 2 liter soda bottle 5. straw OK... This is so you can get really high quick if You doesn't have alot of options on smoking devices.. Take the knife and coke bottle and cut about 4 inches from the bottom all the way around. unscrew the cap. Fill a sink or bucket or anything that will hold enough water you can submerge the coke bottle (a tea piture will work if its big enough). Then take the apple and carve a bowl in the top of it were the stem is. Set the screen in the bowl *(make sure not to cut the apple as so the screen will fall through ie bowl has to be no bigger than screen.) Cut about 3 inches off the straw *(depends on how big the apple at hand is of-course) and force it through the bottom of the apple so it links up with the bowl. Then pull the straw out about a inch or so that way it doesn't melt when you smoke. Then submerge the bottle in the water, when its fully submerged set the apple on top of the bottle so that that it indents the apple about 1/2 inch so that its air tight. The bowl is carved in the top of the apple, the straw goes through the bottom of the apple, then the apple is forced onto the top of a coke bottle that way it is air tight. Hold the lighter over the bowl and pull the bottle up and watch the smoke fill into it, when pulling the bottle up you need to watch the speed and fire to get the perfect hit. *Tip - Don't just stand over the bottle and inhale, push the bottle down in the water so that it force's the smoke into your lung's. What do you think?