Control of passage of magnetic field (2) through materials that block passage through magnetic field (2) is achieved in that in the space in front of permanent magnet (1) is set a construction assembly (3) made of sides (4) that are closed, that according to the properties of the material that the construction assembly (3) is made from and the side (4) prevent further passage through magnetic field (2). By moving the sides (4) of the construction assembly (3) in the meaning of opening an opening (5) is opened on the construction assembly (3) that prevents passage through magnetic field (2) through construction assembly (3). Control of the very diameter of the opening (5) by means of sides (4) of the construction assembly (3) reduced or increased passage of magnetic field (2) is set, enabling hereby control of the passage through magnetic field (2) through materials that block passage through magnetic field (2), i.e. construction assembly (3).
