Nikon D780 DSLR Camera (Body Only) - Manual (Page 136)

90 Camera Controls
A Protecting Pictures from Deletion
During playback, the Q / g ( U ) button can be
used to protect pictures. Protecting pictures
helps prevent accidental deletion.
A Viewing Help
Where available, a description of the currently-selected item can be
viewed by pressing the
Q / g ( U ) button ( 0 62).