Organize your content usually vertical, but some have an additional horizontal or tabbed arrangement, then click to closet. Some will only allow text, but most will allow any content in each collapsible element. It gets tricky if the stack you're using needs to know what size it is before displaying. Styling the boxes and "go" buttons is a feature. Also, Icon decorations. Animation control of the open/close and Go button is a feature with some.

Note: The Foundry 2 theme is used. Where another theme is necessary (F6, F3, Platform) the menu will be replaced by a link to the Accordian home page.