THIS term is applied to cards the backs of which are so patterned that if after they have been arranged exactly the same way of the reversal of a card, end for end, can be detected by the difference in the pattern. The principle is by no means a new one but Charles Jordan was probably the first to apply it extensively. Annemann and others have also devised some very striking effects that can be done by its aid. Probably the best cards for its use are the Bicycle League Back cards No. 808. In the center of the backs of these cards there are three wings forming a sort of triangle. Holding a card one way the center wing points to the right, but on turning the card around the other way the wing points to the left. The difference is plain to anyone looking for it, indeed a reversed card can be detected at a distance of several yards, yet it will never be noticed by the uninitiated. It will at once be seen that having a pack with this mark pointing the same way on all the cards any card placed in the pack after it has been reversed can be found with ease no matter how much the pack has been shuffled. Many of the modern bridge cards can be used in the same way as long as the pattern is not too strikingly a one-way design. It would be impossible to include all the tricks that have been devised upon this principle. From the following selection the reader win no doubt be able to select many that will appeal to him and perhaps devise others himself, which after all is the most fascinating part of card magic.