This is a very simple recipe and so good! When we have leftover corned beef on hand, the next night we know immediately what our next lunch or supper will be! My mom used to make these for us all the time and this recipe is our favorite for making Rubens. The flavor of the usual Thousand Island Dressing is too sweet for our tastes, so we use a little mayo and mustard in its place. The results are wonderful and I hope you will agree. However, if you prefer, use the thousand island dressing, your choice! Serve with some chips of choice and a dill pickle. If you don't have homemade corned beef on hand, you can buy it presliced in your grocer's deli.