I don't interesting in shortcuts. I want to do it by dragging windows.
Making the assumption you are using xubuntu 14.04 there are a couple of GUI options you could explore:
Using the Window Manager - Advanced options you can disable the scrolling of workspaces when dragging the window left and right. This will tile the window on these borders.
Alternatively if you dont use workspaces, by simply reducing the workspaces to 1 then windows will automatically snap to left and right
If you are using xubuntu 12.04 then tiling is not a built in option for the window manager. See the linked question for a workaround for this