Sometimes you may want to see two or more windows at the same time. ratpoison allows you to split the display into frames (see Concepts). Each frame can then contain 1 window. To split the current frame horizontally use C-t s. To split the current frame vertically use C-t S. If you have enough windows, you'll notice that the new frame will find a window for itself. You can now use the normal navigation commands to switch windows in the frame. Note, however, that if you switch by name or number to a window that is already in another frame, you'll switch to that frame.
Before too long, you'll probably want to switch to another frame. Use C-t tab to cycle through the frames. If you want to remove a frame use C-t R. ratpoison automatically adjusts the size of the other frames to take up the free space. Unfortunately ratpoison may not always fill it in the way you might like it to.
Finally, when you've had enough of the splitting and you just want good ol' full screen ratpoison press C-t Q to remove all splits and leave you with the current window full screen.