A bottom seal, at the lower end of a step screen, is adapted to convey solid particles and other objects positioned in flowing water. The step screen has a grating including alternately fixed and movable lamellar rods with intermediate gaps to allow the water to pass through the grating. The bottom seal extends substantially across the entire width of the grating to seal the ducts that arise between the fixed lamellar rods at their lowermost step as the movable lamellar rods move upwards between the fixed lamellar rods. The bottom seal includes an elongate bottom cover, which at its longitudinal edge upstream is, via hinges, pivotally connected to the step screen via a bottom step upstream of the bottom cover. At its longitudinal edge downstream, the elongate bottom cover is guided on guides on the lowermost steps of the movable lamellar rods in order to follow the motion thereof and, in this motion, is pivotable up and down close to and past the edges upstream on the lowermost steps of the fixed lamellar rods.