To improve the probability of arresting a criminal by making the fleeing criminal fall down.

A method for dispersing many rings or ring-like molded substances to the surface of a floor and, when the runaway steps on a ring, erecting the aperture of the ring, catching the other foot stepping on the surface of the aperture to make the runaway fall and interrupt the runaway for crime prevention is devised. The shapes and materials of the rings to be used for the method should satisfy requirements that the ring is not kicked away by the stepped foot and the ring should be erected when the ring is stepped on. A runner or a walker is made to fall down by controlling the requirements of the shapes or materials. Since the dispersion of many rings is required, a dispersion device consisting of a storage part for storing rings to be dispersed, a dispersion port, a device for opening the dispersion port, and a control device for the opening device are devised.