The membrane is a thin, almost sheer protective layer covering the bones. Some people leave the membrane on when cooking because they enjoy the crackle that it produces when cooked. Others swear by removing the membrane to allow the rubs and sauces from penetrating the meat. If you choose to remove the membrane, use a butter knife to gently separate the thin membrane layer that holds the bones together and the thicker top layer that you wish to remove. Gently pull the two layers apart, and, gripping the top-layer edge with a paper towel, tug the membrane until it separates from the rack of ribs.