Sealing equipment is categorized according to the method used to seal a bag or pouch. Bags can be created from various materials such as paper, plastic, cotton, and other fabrics. Different sealing methods can be used depending upon the bag material. Bags may be sewn, pasted, or, in the case of plastic, heated, and pressured shut. Paper bags are available for loose items like flour. Plastic bags are used for bread and merchandise. Cotton or other fabric bags can be used to ship loose items. Bag sealers may also be used to shrink wrap products in heat tunnels before they reach the heat tunnel. Bag sealers do not only seal bags; they may also manufacture bags from scratch as each closure is sealed. There are two types of bag sealers, automatic and semi-automatic. The first automatically seals the bag and tucks any flaps, while the second needs somebody to manually feed the bag into the sealer to close it and tuck any flaps.