Quadrangular shelving comprising four bars with sets of four first pairs of holes, wherein the location of said sets defines different heights of the shelving for establishing the quadrangular trays, a set of quadrangular trays, wherein each tray comprises four corners and wherein each corner forms an opening and comprises a second pair of holes, the shelving comprises for each tray of the set of quadrangular trays: four plates, a pair of screws adapted to screw each plate and wherein the plate covers the opening.