Abstract: The invention discloses a method for temper hardening flat metal products, comprising the following steps:introducing a flat product coming out of the furnace into a temper-hardening bay, depositing this flat product on supporting elements forming a lower substantially horizontal supporting table, causing a sudden cooling of the flat product in the deposited position, by spraying a temper-hardening liquid simultaneously on the whole of its upper surface and on the whole of its lower surface, removing the flat product from the temper-hardening bay, and further, before the sudden cooling, transferring retaining elements forming together a substantially horizontal retaining table to a horizontal retaining plane at a predetermined distance above the upper surface of the flat product and, during the sudden cooling, optionally retaining the flat product on the upper retaining table, within the limits imposed by the said horizontal plane. The invention also discloses a device for implementing this method.