<human>:  Why did the Vikings use a clinker-built ship?
<bot>: A clinker-built ship is one in which the planks are joined together with wooden pegs. This type of construction is called a clinker-built ship because the planks are joined together using a type of wooden clinker. This type of construction was first used in the Viking era. The Viking ships were extremely seaworthy and fast, so they were used for trade and raiding.