Tying a Roast with String
Tying a roast helps ensure that it will cook evenly. A tenderloin, for instance, tapers into a tip, so unless you tuck it under and tie it, the tip will be over-cooked when the thicker portion is done. You may also want to tie a roast because you have cut a pocket in it and stuffed it, or put a filling under the skin that you want to hold in place.

To tie a roast, you can cut little strings and tie each one around the roast separately. Or, you can simply tie the roast like a package with the strings crossing at 90º angles. But the "proper" way to tie a roast is to cut a single, long piece of string. Place one end under the roast, about 1 inch from the end. To prevent the string from slipping while you tie the first knot, pass the short end twice around the long end instead of once. Then pull both ends to tighten. It will hold in place while you finish the knot.

Then plant your finger in the center of the meat 1 inch or so below the first knot. Pull the string around your finger, then lift up the roast and pass the string under it. Thread the long end of the string under the string held by your finger. Now you have two parallel ties around the roast. Again plant your finger an inch or two below the second tie, and repeat until you work your way down the entire length of the roast. Then pass the string under the roast lengthwise, bringing it back to its starting point, and tie it off.