If sidebar.float.type is “none”, then no float is used.

If sidebar.float.type is “before”, then the float appears at the top of the page. On some processors, that may be the next page rather than the current page.

If sidebar.float.type is “left” or “start”, then a left side float is used.

If sidebar.float.type is “right” or “end”, then a right side float is used.

If your XSL-FO processor supports floats positioned on the “inside” or “outside” of double-sided pages, then you have those two options for side floats as well.