Dell U3821DW 37.5" 21:9 Curved IPS Monitor (Silver) - Manual (Page 69)

Operating the monitor
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Using the tilt, swivel, and vertical extension
NOTE: The following instructions are applicable only for attaching the
stand that was shipped with your monitor. If you are attaching a stand
that you purchased from any other source, follow the setup
instructions that were included with the stand.
Tilt, swivel
With the stand attached to the monitor, you can tilt and swivel the monitor for the
most comfortable viewing angle.
NOTE: The stand is not installed at the factory when shipped.
Vertical extension
NOTE: The stand extends vertically up to 120 mm. The figure below
illustrates how to extend the stand vertically.