Screening for classifying a material

A screening or screen for use in classifying material. The screening includes a plurality of warp screening elements. Preferably, the plurality of warp screening elements is a plurality of warp wires. The plurality of warp screening elements includes a first warp screening element having a plurality of horizontal undulations. The plurality of warp screening elements further includes a second warp screening element. Preferably, one of the first warp screening element and the second warp screening element is a shaped wire having two substantially flat sidewalls. At least one retaining member is operably associated with the plurality of warp screening elements to form an integral screen segment having a plurality of openings for permitting material to be classified to pass through the openings. The first warp screening element has a cross-sectional height or shape different from the cross-sectional height or shape of the second warp screening element.