It is used to adjust the roll gap so that the rolling stock can reach the required section size. The upper roller adjustment device is also called a "press-down device" and is available in manual, electric and hydraulic versions. Manual reduction devices are used on profile mills and small mills. Electric depressing devices include electric motors, speed reducers, brakes, depressing screws, depressing nuts, depressing position indicators, spherical spacers, and pressure measuring instruments; its transmission efficiency is low, and the rotational inertia of moving parts is large. Slow speed, low adjustment accuracy. Since the 1970s, after the AGC (Automatic Thickness Control) system was adopted for strip rolling mills, hydraulic pressure reduction devices have been used on the new strip cold and hot rolling mills and heavy plate mills, which have the advantages of small thickness deviations and high product qualification rates. .