C-a F
fit
Change the window size to the size of the current region. This command is
needed because screen
doesn't adapt the window size automatically if
the window is displayed more than once.
If, for example, you are using two SSH clients and sharing a terminal with multiuser on, if one screen is too small, they can press C-a F and the window will be resized to fit their terminal, leaving the larger screen with blank space to fill the unused space.