screens stop ash and bud going into the water.
screens make sure you dont waste bud by "plugging" the bowl with a bit of nug
and subsequently it goes into the water. (fucking retarded IMO)
screens are just common sense, but most american tokers seem to not use them.
the worst excuse ive heard is "they dont stay in the bowl.".
my answer to this is "dont be a complete imbecile, you clearly didnt try.
if you had you'd have realized you need to smoke out of it properly before
the screen will stay in place due to resination.".