A large cotton or mixed fibre sheet used to cover furniture, to protect the wood or upholstery against dust; most often used during refurbishment and re-decorating projects to keep gritty dust, dirt, paint and other detritus from damaging walls, floors, cupboards and all furnishings.
Don’t bother too much with the sides and hems, as these are to some degree finished–just hook the fabric up with safety pins, or hand stitch over rings or a pole. Alternatively, for a slightly longer term objective, and to keep draughts away at windows and doors, make them up with interlining and lining–but don’t worry about particular locking in and too much detail. You could even just cut all layers to the same size and tack through to hold them in place. When it’s that casual, keep it casual.