Abstract: A screening system with knocking devices includes a screen panel support, connector bars, knocking devices, and screen panels. The knocking devices are generally spherical-shaped balls held by elastic arms connected to the connector bars. When the screening system is activated by moving material onto the screen panels and vibrating the screen panel support, the knocking devices bounce around the undersurface of the screen panels and prevent the build-up or jamming of material blocking the openings in the screen panels. The knocking device and screen panels are separate so that when one of those elements becomes defective, the screening system can be fixed without replacing both elements.