A screen system for improving a vibrating shaker apparatus for separating drilling fluid and drill cuttings is described. The screen system comprises a dual screen having a coarse mesh upper screen attached to a finer mesh lower screen with a channel between the two screens. One or both of the screens may be wedge shaped to affect the flow rate of drilling fluid and drill cuttings across the screen. The screen systems can be installed in existing shaker apparatuses using various attachment systems, such as wedge clamping systems, hydraulic or air pressure clamping systems, or hook screen systems.