The gravity feed chute has a firebox/ash box at the bottom. Near the top of that box there is a grate that holds up the charcoal, about 2-6" above that there is an opening into the cooking chamber. The air comes in the ball valve and flows threw the coal and the hot air continues threw the opening into the main cooking chamber. As the charcoal burns up the ash falls threw the grate into pan leaving fresh charcoal sitting on the grate. As it feeds itself down it is constantly lighting new coal. The key to the whole operation is the door on top where you feed the charcoal into must be 100% air tight to keep the coal from burning up the chute. This allows only the coal between the great and opening to the cooking chamber to burn as there is no oxygen above that point. Hope this helps, I will see if i can find some pics for you.
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