The events in The Dragonslayer of Edgewhen take place in 1002. At that time, situation is as follows:
Ports on the Yarl River System
The Clanfolk control all the busiest ports on the Yarl. They have an outpost at Dashar on a river that eventually feeds into the Kailanarl and then to Brin. They are also building a presence on the delta where the Yarl empties into the Sunward Sea.
Children of Justice have a stronger presence at the delta and their trade routes extend all through the Sunward Sea. But these Children of Justice are civilized “Bluefolk”. Their culture is different from that of the “Riverfolk”, who live a nomadic life on the system of rivers accessible from the Yarl.
Civilized Stripedfolk have some ports on the Yarl, but much of their trade is focused inward. (These are the plow-people along the Dothedarl, whom Summerwind scorns.)
The laws of the river have been set by the Clanfolk, because they have the most ports.
The Clanfolk love trade agreements. Or even disagreements, if they provide something to bargain over.
Each city-state has tariffs and dock fees to protect local merchants. And each city-state has agreements with certain trading partners that provide special exemptions to these fees and tariffs. In order to tell whether a merchant qualifies for an exemption, the dockmaster has to know where the merchant is from.
Clanfolk do not have passports. It is very easy for them to lie about where they are from. But the boats do not lie. Because the prow of the boat is branded.
Under river law, a boat marked by a city’s brand is entitled to all the benefits of a trade agreement negotiated with that city. In theory, the merchant and his goods should be from the same city-state as the boat. (In practice, the merchant just needs to pay a commission or fee to a cousin who lives in that city-state.)
Once brands were in wide use, river travelers began using them for identification on the river. But the brand in the wood was difficult to see. So boats began adding a larger, painted mark. This enabled merchants to identify a boat’s city-state at a distance.
Once painted marks became wide-spread, it did not take long for merchants to start marking their boats with clan symbols as well. These were even more useful: A merchant from the same city might be a friend or he might be a rival, but a merchant from the same clan is always a cousin.
In 1002, the clan mark is the most visible from a distance, but city marks are still painted on some boats, by tradition. Neither of these marks is required. The dockmaster is concerned only with the city brand.
Accidents, Aid, and Abandonment
Boats sometimes run aground on sandbars or snag on submerged trees. People sometimes fall off their boat into the river. Under River Law, a boat must give aid to a boat or person in distress, unless such aid would put the rescuing boat in jeopardy.
An abandoned boat and its cargo still belong to the owner if the brands are visible. An owner can voluntarily relinquish his claim by obliterating any visible brands. This is usually accomplished by painting them with tar. Hence the expression “to tar the brand” which means “to give up”.
Cargo outside a boat is fair game, as is anything that can be salvaged from a boat whose brands are submerged.