Not really a Magic Trick,But still it helps

To Leave a Prearranged Pack Undisturbed While Seeming to Shuffle It Thoroughly

The pack is held lengthwise in the right hand between the thumb at one end and the second and third fingers at the other, the forefinger bent over the upper side. The left hand, palm upward, is under the pack. The right hand drops a few cards from the top of the pack into the left hand, which places them at the bottom of the pack, where they are held by the right thumb, assisted by the second and third fingers, as shown in illustration, Fig. 22. Again the right hand drops some cards from the top into the left hand. Then the right hand appears to drop more cards in front of those in the left, but merely goes through the motion without dropping any. Then a few are really dropped but behindthose in the left hand, and this is continued, pretending to drop them in front and really dropping them behind until all the cards in the right hand are used with the exception of the first parcel which is dropped in front (the top) of the pack.

Fig. 22

The pack is now in the order it was before the shuffle. To heighten the deception the cards in the left hand should be kept moving backward and forward. When cards are apparentlydropped in front of the cards in the left hand, the left thumb pushes the cards already in the hand toward the fingers, and when cards are really dropped behind those in the left hand the fingers tilt them back toward the thumb. This tilting motion is continued until all the cards in the right hand are disposed of.