There used to be these pipes designed so that they had a chamber between the bowl and the mouthpiece end. Some were wooden and had a little door you could slide open and others had a stem that screwed apart to reveal a big chamber inside the stem. People used to put a few buds in there to act a a kind of "filter," but the real reason seemed to be to get a bud totally covered in toxic layers of goop. The when you were out you could pull out the stinky, resinous, glop-soaked bud and smoke that. It alwasy did the trick. I don't thnk anyone uses those anymore.