— Command: width [-w|-d] [cols [lines]]

(C-a W)
Toggle the window width between 80 and 132 columns, or set it to cols columns if an argument is specified. This requires a capable terminal and the termcap entries ‘Z0’ and ‘Z1’. See the termcap command (see Termcap), for more information. You can also specify a height if you want to change both values. The -w option tells screen to leave the display size unchanged and just set the window size, -d vice versa.

— Command: height [-w|-d] [lines [cols]]

(none)
Set the display height to a specified number of lines. When no argument is given it toggles between 24 and 42 lines display.