1. Safety tips:
a). In case of being shaken, dismantle the device before up-down.
b). In case of sliding, lock the handle tightly (like 4th sign), to adjust up-down by loosing one teeth. Grasp the up-down handle (like 5th sign) first, for stability before pressing on the positioning pin (like 6th sign).
c). Step on the moving up-down pole (like 7th sign) during movement. Moving can be achieved by loosening the positioning screw and setting out the required positioning height, when the floor is not smooth.