It is the combination hot air rising and subsequent vacuum effect in the room below which ensures that smoke from a fireplace fire will go up a chimney. without the control of the chimney flue, this effect could quickly lead to a fireplace fire getting too hot for the fireplace to handle.
oilcloth. (textiles). A fabric coated with a mixture of oil and clay, used as a waterproof covering. A floor covering made of a heavy fabric treated with oil paint.
Definition of sailcloth. : a heavy canvas used for sails, tents, or upholstery; also : a lightweight canvas used for clothing.