A Block Visibly Slowly Diminishes and Vanishes right before Spectator's Eyes!

A yellow block of wood 2 1/4" in size is placed between two black blocks of the same size in an open frame cabinet.  Taking hold of the black blocks and pushing toward the yellow block the yellow block diminishes in size until it vanishes completely!  The yellow block is then produced from a hat or made to reappear elsewhere.  Measured from the base this is 8 1/4" wide x 3 7/8" deep x 3 1/4" high not including the handle.  Includes instructions. Condition very fine.