A plurality of teaching identification face image patterns of teaching persons are obtained in a first pattern obtaining process using an image scanner, and a plurality of teaching video face image patterns of the teaching persons are obtained in a second pattern obtaining process using a video camera. Receiving a set of first samples and training a first statistical model base upon the first set of samples, where the first statistical model is of the same class as the trained statistical model. The knitted mesh has a mass density of less than 20 gm2. A radially inwardly projecting actuating bump formed in the movable part bears in the latched position radially inward on the block and holds the block in the inner position.