EO.Web Splitter can display a collapse button on splitter divider. The left/top pane completely collapses when user clicks the button. Once the pane is collapsed, the button is switched to an expand button, which can be used to expand the pane into its original width when clicked.

To enable collapse/expand button, set the splitter's CollapseButtonImage, CollapseButtonHoverImage, ExpandButtonImage, ExpandButtonHoverImage. To set the location of the button, use ExpandCollapseButtonAlign.