I've been randomly sailing around the various continents and I have noticed that a large number of thingwalls have a small palisade box with no entrance or exit built nearby. What is their purpose? I've found at least ten so far and this is no small expenditure of time to create them, but I do not know why someone would build it. Typically there is no hearthfire or village nearby.
My guess is some form of griefing? Do thingwall travelers land in them and can't use the thingwall to get out? Except that person could simply hearth home in that case, unless I am missing something.