Disappearing the Tower

MATERIAL-Color cardboard, Tower which you want to disappear, Pencil, cutter
PROCERDURE-Take a color cardboard & border it in the shape of rectangle with the help of the pencil. Take the cutter & cut it in the shape of the rectangle & open it. Take that cardboard to that place where the tower is. But the background should be sky. Show the tower from that rectangle after showing to the audience close that rectangle shape cardboard & take that rectangle to the place where there is no tower but only the sky. Open the rectangle & show to the audience. The tower disappears.