I see that my instructions were confusing users. So I made changes to clarify. The purpose to removing the LCD panel was simply to verify that the Stand riser vertical riding slot was functional. On the Stand riser itself, see the vertical riding slot below the square mounting bracket. [IMAGE]   That vertical riding slot shows the allowable up/down movement of the connected LCD panel. The LCD panel is attached to the Stand riser. If it is already all the way up, you can only go down. If it is already all the way down, you can only go up. There are no buttons. You simply grasp the top and bottom bezels of the LCD panel and push or pull up and down.  
I also cannot figure out how to adjust the height of this monitor. Very frustrating.  
U3421WE, how to adjust height? #3