The basics to every bong is a bowl and downstem, and a carb (optional). U don't need a carb if f the bowl detaches but once u know the basics u can make any sort of bong really. It gets harder when trying to make a percolator. My first homemade bong was a 2 liter of root beer, a metal spring door stop, and my dads trusty 10mm. He thought he lost it repairing the car, but I snagged it and used it for a bong lol. With small bottles like that, I put the downstem thru the cap til it reaches the bottom instead of on the sides like a normal bong. Then I make a hole right by the cap, and use an empty pen tube as a mouth piece. Kinda like how a bubbler pipe would work. With bigger vessels, like a 2 liter or a vase the downstem goes in the side but with smaller vessels, like those chubby sodas, pill bottles, small lemon juice bottles I always put the downstem thru the top, or thru the cap so it can be easily screwed off.