Baskets have many uses, but how they are used is often dictated by their shape. Burden baskets are almost exclusively twined and conical. The weaving style of a basket can also be indicative of its function. A tighter weave is needed for cooking and sifting, whereas a more open weave is needed for winnowing. An open weave also takes less time to produce and can be used to make baskets that are not intended for holding liquids or small items. In some cases, baskets that are meant to hold liquids are coated in pine pitch to make them leak-proof.