Self-working tricks are usually based on clever mathematical principles. Some of these mathematical principles, like the Gilbreath Principle, are so subtle that a performer may know how to carry out the procdures, but may not understand how or why they work.

Of all the self-working tricks, the Trapdoor Card, by Robert Neale, is the most baffling. The effect is very visual and looks completely impossible to accomplish. This is based on another branch of mathematics called topolgy, which is the study of the inside and outside of things.

The “Magical Up-Down Arrow” is another topological trick and looks impossible to explain.

In effect, a strip of yellow paper has a cut-out of an arrow in the centre, and 2 rectangular cut-outs at its top and its bottom respectively. A narrow strip of black paper is inserted through the 2 restangular cut-outs so that the yellow paper is now loosely attached to the black strip.

The cut-out arrow on the yellow paper is pointing downwards. The performer attempts to bring this arrow pointing upwards without disengaging the yellow paper from the black strip, or revolving the entire structure 180°.

To prevent the performer from turning the entire paper structure, a spectator holds the top and bottom edges of the black paper strip. The performer can now only manipulate the yellow paper that is attached to the black strip. The performer folds the yellow paper several times around the black strip. When the yellow paper is unfolded, the cut-out arrow is now seen pointing upwards. The black strip is not moved at all during this procedure. The result seems totally impossible.

You receive both the yellow and the black strips of paper. A link to a video tutorial is also provided.

Once you get the knack of the folding procedure of the yellow paper, you can perform this effect wihout any problem. You will be amazed yourself that it works. Do not bother to try to understand how it works – you are likely not able to.

Both strips of paper are made of ordinary grade of paper and they will be worn out through multiple performances. Using these 2 papers as templates, you can made new ones by using coloured papers purchased from the stationery store.

A visual and impossible-looking effect that is easy to do. You will want to have this in your performing repertoire.

(Rated 4/5 stars)