Canon Speedlite 600EX II-RT Manual (en)

By pointing the flash head toward a ceiling or wall, the flash light will 
bounce off the surface before illuminating the subject, making it 
possible to soften the shadows of the subject for a more natural-looking 
shot. This shooting method is called “Bounce flash photography”.
Set the Bounce Direction
You can turn the flash head while pressing the <z> button as 
shown. When you turn the flash head, the display changes to <m>.
When the flash head is turned with the flash coverage set to <L> 
(automatic), the flash coverage is set at 50 mm and <
> is 
You can also set the flash coverage manually (p.38).
m Bounce