Plain, undyed cotton string, strong enough to hold a tied roast and safe at oven temperatures, used to truss poultry, tie a boned joint or rolled fillet into an even cylinder, secure stuffing and bundle herbs for a stock. Also sold as kitchen twine or cooking twine. Tying meat into a uniform shape makes it cook evenly and slice cleanly; a trussed bird keeps its legs and wings close to the body so they do not dry out before the breast is done.
Only untreated cotton or linen belongs in the oven: synthetic string melts and polished or dyed twine can shed into the food. The twine is cut off before carving.