On the back of the ribs, you may see something called a membrane (it will look smooth and shiny). This membrane can be removed, it is up to you. I find cooking ribs in the slow cooker (as opposed to grilling or smoking) tenderizes the ribs to the point that you can easily eat this bit of the rib with no problem. But, a lot of people like it removed because they find it a bit chewy. I think it helps hold the ribs together better while slow cooking in the crock pot. You can take a small knife and make a small incision underneath it. Then get your fingers underneath it and pull it off. Check out my post on How to Grill Pork Ribs for picture instructions on how to do this.