An application of the tap principle to the spelling of numbers was made by mathematician and magician Royal V. Heath c. 1925 when he marketed Tappit. It works by a self-working mathematical method which has been applied to a number of effects over the years.
(Notice: The colors should be: white, red, blue, black, green, yellow, but some colors have faded over the years, in particular the white tile is now the same color as the yellow tile which both look orange today.)
Effect: Six Catalin or Bakelite tiles, are shown, blank on one side with a different number on each of the faces. The performer leaves the room while a spectator secretly makes note of the number on any one block, finally turning all six blocks face down on the table and shuffling them around as much as he desires.
The performer is called back, he starts to tap various blocks with his pencil-the spectator at the same time mentally spelling out (silently) his selected number, one letter for each tap-and on the last letter the spectator calls “Stop.”
This is done, and in some mysterious manner, the performer’s pencil is always on the block bearing the chosen number. No gimmicks are employed with these blocks which are in very attractive colors and highly polished but free from preparation of any kind.
Easy to do but hard to detect even with repetition.
(Notice: Includes: Printed Instructions.)( Post Source: martinsmagic.com - click for details )