The control of temperature distribution across the strip is essential for the hot strip flatness improvement. Hot strips of Arcelor in Avilès may display wavy edge defects that are generated after the finisher and are attributed to residual stresses introduced by the accelerated cooling on the run-out-table. A first approach has established that the thermal drop on the run-out-table has a significant effect on flatness, at the edges in particular. Among several systems that may control temperature at the edges, the edge masking technology has been selected, considering the previous implementation on CSP mills. Wavy edges are considerably removed or even suppressed on the operator side, while they are reduced but not eliminated on the drive side.