When you ask the question, "Can the scroll-bars of a browser be removed in some way, rather than simply hidden or camouflaged", everyone will say "Not possible" because it is not possible to remove the scrollbars from all browsers in a compliant and cross-compatible way, and then there's the whole argument of usability. For track pieces it indicates whether the track piece abuts a singleton button. The particularly nice bit here is that the scrollbar is on the body element, yet the scrollbar isn't stuck to the top, bottom, or right edge of the browser window as scroll bars normally are. It is used to detect whether a button is part of a pair of buttons that are together at the same end of a scrollbar.