A brown kraft sack is a paper bag that has been treated with a brown kraft paper. This gives the bag a rustic look and feel. The paper is also very durable, making it ideal for use in a variety of applications. Brown kraft sacks are often used as shopping bags, as they are strong enough to hold a variety of items. They are also popular as gift bags and for packaging food items. Brown kraft paper is also used to make a variety of other paper products, such as envelopes and paper towels.