Shale shakers are the primary solids separation tool on a rig. After returning to the surface of the well the used drilling fluid flows directly to the shale shakers where it begins to be processed. Once processed by the shale shakers the drilling fluid is deposited into the mud tanks where other solid control equipment begin to remove the finer solids from it. The solids removed by the shale shaker are discharged out of the discharge port into a separate holding tank where they await further treatment or disposal.