If you want to draw the custom header for a C1SplitterPanel or draw the custom Splitter Bar you can use the DrawHeader and DrawSplitter events.

The DrawHeader event is fired when the C1SplitContainer control needs to repaint the header of the specified C1SplitterPanel. The clipping region is restricted by the panel header area.

The DrawSplitter event is fired to draw the splitter element (the user can drag this element to resize the panel). The clipping region is restricted by the splitter element.

You can take a look at the LayoutDemo sample for an example of using both events.