Use this command to move the cursor to the horizontal or vertical splitter between panes of the active MDI child window in the client area. With the splitter selected, you can move the splitter to resize the panes. (You can also select a splitter by clicking on it.)
For example, a program document window contains a vertical splitter between the Tests view and Tasks view, and horizontal splitters between the test header and test code view. If one of the objects in Tests or Tasks view is highlighted, the Split command selects the vertical splitter between these two panes. If one of the objects in the test header or test code view is highlighted, the Split command selects the horizontal splitter between these two panes.