Sold as a pair
Like all Surly products, there's built-in useful details. For example, the deck-attachment bosses stick up from the rails to create space between the deck and rails, providing windows to route tie-down straps and cordage; and threaded bottle cage bosses located at the rear of each rail provide mounting locations for accessories: bottle cages of course, or lights, cameras, pumps, flags, horns, etc... Dummy Rails will work with cargo frames (including the Surly Big Dummy) built around Xtracycle's longtail standards.