Defined
The circle and square boxes are a two-part magician's accessory, made withe an outer square box with no bottom and no top, and an interior circle tube with no top or bottom. Some boxes sit on a thin platform, whereas others have feet and offer an empty space below the boxes, which makes the illusion even more interesting. The outer square box is often made with a see-through acrylic window on the front. The purpose of this window is to allow the audience to see that there are no hidden compartments. The cylindrical tube is detachable and has no top or bottom, so the audience sees there is no hidden compartment in this circular box, either. This circle sits inside the square box.
Illusion
To start one of the tricks, the magician removes the square box from the platform and shows both its top and bottom to the audience so they can see there is nothing in the box and no hidden compartment. He replaces the square box and does the same for the circle box. Once the boxes are back in place, he starts to pull out items from the cylindrical box. These can be scarves, coins, cards and, in some cases, even a rabbit or bird.
Secret
The trick to the illusion lies in the secret compartment that appears between the square and circle box when the circle box is placed inside the square. The magician can place and pull objects from this secret compartment.
Sizes
This magician's accessory comes in different sizes. Smaller boxes are about 8 inches wide by 12 inches tall, with a load capacity of 5 inches wide by 11.5 inches tall. This allows you to pull out items that are about 4 inches wide by 7 inches tall. Larger boxes made for professional magicians are approximately 17 inches wide by 23 inches tall, giving you a load capacity of 12 inches wide by 22 inches high, which is more appropriate for pulling out rabbits, doves and other larger items.