Abstract: The invention relates to ore screening machines having longitudinal bucker bars 17 spaced transversely across a screen box with transverse rails 1 spaced longitudinally along the screen box and supported on bucker bars. The transverse rails have a tension member 5 embedded therein which is connected to a C-shaped connecting member 6 at each end thereof. The C-shaped connecting members connect with hook members 7 which in turn connect with a clamp 9 which is secured to each side wall 14 of the screen box to apply tension to tension member 5. The bucker bars and transverse bars forming a grid structure to support screen modules 18 seated on the transverse rails 1 to provide a screen mat extending across the screen box.