Invite a lady from your audience to assist. Show the napkin both back and front leaving your spectators with no doubt that it is a perfectly ordinary article. The magician then brings the four corners together to form a neat little bag. The article to be vanished, lets say a borrowed finger ring or bracelet, is shown around and placed into the bag. The lady holding the bag is requested to feel the ring through the folds of the napkin. After suitable by-play, the magician whips the napkin from the ladies grasp and the article HAS VANISHED! The vanished item is later found in some other object, safe and sound.
Should you wish to perform this routine with a borrowed article from your audience, you will find that the vanished article can easily tip from the special pocket as the napkin is placed down on the table, you can then load it into a nest of boxes or other prop.
If you look in "Magic Books", you will discover many other clever notions using this versatile prop.