No person, partnership or corporation shall exhibit to the public or to spectators in the City, for money or other reward demanded or received, any motorcycle operation, speeding or racing in any stadium or motordrome having a saucer track, unless such saucer track has constructed entirely around its rim or periphery, a metal screen or shield placed at such angle toward the center of the stadium or motordrome as will effectually prevent a motorcycle, at whatever speed operated or however directed, from passing beyond the rim or periphery of the track and into the portions of the motordrome or stadium designed or used for the accommodation of spectators. Such screen or shield shall be of such strength and so braced by metal supports that a motorcycle cannot break through it any place. The width of the screen or shield, the kind of material used in its construction and the angle of its direction toward the center of the course, shall all be such as are approved by the Commissioner of Building and such as will in his or her judgment, accomplish the purpose of safety to the public intended by this section.