A real chillum (of Indian origin) consists of a clay cone, and a 'stone' (a clay stick that fits inside the cone. There are small gaps between the stone and the inside of the cone to allow smoke thru. Once the stone's in the cone, there's about an inch deep gap at the top. You fill this with your choice of herb, put a bit of thin cloth over the toking end to stop bots of ash coming through, light up, and hit the motherlover! It's pretty basic, but they look quite cool - my bro brought me back one from Rhajisthan