Abstract: A sizing screen for sizing particulate materials, for example, is provided which uses a plurality of wire loops arranged to define a plurality of parallel wire strands extending between a first end and a second end of a screen frame. The frame has anchor means mounted at its first end and tension means at its second end. In the simplest form of the invention, pairs of wire strands are adjusted simultaneously by the tension means. In more advanced forms of the invention, means are provided for adjusting pluralities of the wire loops, each wire loop adjustment corresponding to two wire strand adjustments. The frame is constructed so that the wire strands have a double crown. One crown extends along the width dimension of the frame, and a second crown extends along the length dimension of the frame. The double crown arrangement promotes more even spreading of material as that material travels along the wire screen and is important in maintaining wire strand position.