The strings you see tied around a piece of meat at your friendly neighborhood butcher shop is called butcher’s twine. The technique is used to hold pieces of meat in compact shapes. This helps the meat to cook more evenly as opposed to having some thick parts and thin parts that cook at different rates. An example of tying for these purposes is lamb shoulder. A boneless lamb shoulder is a flat piece of meat that is fairly irregular in thickness – butchers roll these and tie them for roasting. This technique can also be applied to chickens or ducks; it’s called trussing. The reason you truss poultry is to protect the wing tips of the chicken from burning and over-cooking and also to hold the juices in the cavity of the bird.