Spring Design: The adjustable spring bracket automatically adjusts the height of the gate according to the surrounding terrain during the entire opening and closing cycle, effectively preventing the gate from sagging to maintain the level of the fence line Shock Absorption: Easy to move and roll, making it easier to open and close the gate. Made of high quality rubber and metal, it is sturdy and durable. Spring-loaded design: allows the door to open and close freely by automatically adjusting the height on uneven floors while eliminating door sag. Heavy Duty Casters: Wheels have a maximum load capacity of 220 lbs and can also resist corrosion from chemicals and solvents. Heavy duty universal mounting plate with 4 holes for easy attachment to wooden gates or horizontal or vertical rails along tubular farm gates. Easy to install: Heavy duty universal mounting plate with 3-hole easily mounts to wooden doors with offset bolts, versatile hole pattern also allows for easy installation to tubular farmhouse doors along horizontal door tracks or vertical doors, includes bolts and screws editing.