A jangdok is a container made out of a special clay. Only fresh air can go in and water and other things can't go in. So, it is good for fermentation and ventilation. Because of these reasons, our ancestors filled these containers with kimchi, soybean paste, and soybean sauce, pepper paste and foods like that.

Our ancestors also buried these containers in the ground on winter. If the jangdoks were left outside, then the food could freeze because of the cold temperature. To prevent this, they needed to bury jangdoks in the ground to make it not freeze and make it keep its temperature.