Kitchen string is probably best known for tying roasts. You can also wrap sachets, tie off sausage links, hang yogurt and food items that need draining in cheesecloth tied with kitchen string and tie it around poultry, vegetable packets or stuffed meats to keep them together. It also has uses outside the kitchen as a craft and utility supply. You can hang recipes from a piece strung between two nails, or tie it around butcher-paper wrapped presents for a rustic looking gift wrap.
Tying meats and wrapping whole birds like chicken and turkey helps keep the cut in one shape, cooking it evenly. It also keeps stuffing inside of birds, and you can keep outside ingredients in place, like bacon, pancetta or herbs. This technique is called "barding." You can also reshape meat by folding or lumping it into shape before tying it.
Place the roast flat, lengthwise on a clean work surface. Hold the string taut with both hands and then slide it under the roast and bring the ends toward the top. Tie two overhand knots, left string over the right, to neatly lock the string in place. Lay the string so it rests on the roast lengthwise, then hold the string with your free thumb 1 inch from the knot. Pull the string taut with your other hand without letting go of it with your opposite thumb. Wrap it under and around the roast once again, pulling it taut.
Lift up your thumb and the string, and pass the end of the string in your other hand under the lifted piece. Pull the string up to tighten it. Repeat this process, tying each time you wrap around. When you get to the end, make sure the string is tight, and run the string up the length of the roast, back to the original knot. Slip it under the knot. Pull tightly, but not tight enough to squash the roast into a U-shape. Tie a final knot.
Home cooks may recommend using dental floss, cotton twine or linen twine when kitchen string isn't available. Dental floss typically falls apart easily and cuts through meat and food, according to Cooks Illustrated. Dental floss is also not intended for food use. Colored hardware tine may leach dye onto your food, which changes the food color and subjects you and your family to potentially harmful chemicals, even if they're in small amounts. Linen twine ties well because it holds a knot on its own and pulls from the meat without fuss once it's cooked. Cotton provides a cheaper and comparatively adequate substitute.