Abstract: A closure member for a bin having an enclosure with a closed end and a mouth, the closure member being adapted to be secured to or to form part of the mouth of the bin and comprising two blade assemblies mounted to be rotatable and to extend across the mouth of the bin, means to urge each blade assembly to rotate to an operative position, each blade assembly comprising at least one blade, the blade assemblies being arranged so that adjacent blades of each assembly are vertically offset and overlap to define, in the operative position, a vertical gap between the adjacent blades.