A close up of a trailer corner, on Surly's "Ted" trailer. You can see the rest of the trailer, and the Troll by following the link above, of course.
"The corners feature threaded M6 bosses for bolting on corner stakes or sideboards. We’ll likely offer these accessories in the future, but don’t wait for us. Go to the hardware store or dig around your garage or basement, and make some stuff. Don't be scared. You can do it."
It's a typical Surly design - solid and simple, with standard parts & sizes that you can build up with readily available bits.
Also in the article is their "Troll" frame, built up into a bike - a disc braked, steel dogsbody of a bike, it looks great in what looks to be a similar army green to my LHT.