In this desktop gadget a small neodymium ring magnet mysteriously floats in the air, restrained by a piece of shoe lace. The trick is in a second magnet, hidden in the top beam. A single knot at both ends of the rope fixes the position of the ring magnet.

Print frame and top with 20 to 30% infill, check the right orientation of the magnets and place the magnet on top. Glue frame and beam together enclosing the magnet. If the dimensions of your top magnet are different, just adapt the SCAD file for the top beam.