Samsung LS21DPWAB-XAA - Manual (Page 18)

( ), By adopting a stand that can be rotated clockwise by 90 degrees, users can
view the LCD screen in the Landscape or Portrait position according to taste.
To rotate the LCD panel to the Portrait position, first lift it up to
its maximum height, tilt it backwards and then rotate it
clockwise.
Rotating the LCD panel without tilting it backwards may
damage the LCD panel.
Using ( ), You can adjust the height of the monitor.
If you rotate the screen without lifting it to its maximum height,
the screen may be damaged because the edge of the screen
would hit the floor.
Swivel stand
Using ( ),You can swivel the monitor left and right at an angle of 175° to set
the monitor lengthwise. The rubber under the stand is to avoid the monitor
slide.
Tilt angle