If you add collapseMin button for BorderLayoutContainers and hide contentpanel in a code, that small collapseMin button, that is placed on the SplitBar stays there. It can be seen in Explorer Demo:

http://staging.sencha.com:8080/examples-dev/#ExamplePlace:borderlayout

Try to hide South or West panels by clicking Hide buttons that are placed in Center panel (not the tool buttons), and you will see, that small collapseMin buttons stays there.