From: TvSwivelMount.com

The swivel mount lessens the “ouch” factor of having to reposition screws nuts or shelving when the audience location changes. Special brackets have been devised to assist in this purpose. The swivel mount allows the bus driver to turn the screen to him to administer operator functions and commands, and the mount allows for placement on an awkward area of the interior bus chassis. LED backlighting functions best in an area under direct light, and TV swivel mounts allow for best placement of the monitors in the space.
TV swivel mount possibilities include LCD elevations for groups and entertainment centers to show off deeper blacks, high definition color, and shadow gradations that a ground or counter based TV unit couldn’t deliver due to surrounding light overlap. Bracket placement cants the flat TV in any dirction the swivel allows.
TV swivel mounts can quickly be moved for best placement of the television within a home or office where server signal is best, swiveling the monitor screen easily to all audience vectors. A TV swivel mount also extends the performance and enjoyment for a fixed or stationary plasma or LCD screen unit.