The mideaval timmes was Kökar's time of greatness. Kökar was then an important port on the journey to and from Reval (Tallinn). At that time Silors prefered to sail close to the coast.

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The cargo ships in the 1100s and 1200s were not so seaworthy that one would go too far from the coast. Hard weather could cause problems. The risk of pirates was also a reason for staying close to land. In addition the space for the crew in the ships was small. It was preferable to cook and sleep ashore.

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There is a sailing description from the 13th century preserved, usually referred at as "King Valdemars passage" because it is linked to the Danish King Valdemar Sejr. The sailing description starts at Utlängan i Blekinge then closely following the Swedish coast up to Arholma in the Stockholm archipelago. It then passes through Åland to Finland and then finally reaches Reval (present Tallinn) in Estonia. The route served as a trade for Danish and Swedish merchants.

 

During the 1300s and 1400s, when the Hansa took over the trade and sailed with the larger cog, they often chosed the straight route over the Baltic Sea, from Lubeck via Visby to Tallinn or Riga. However, The fairway of King Valdemar continued to be important for trade between the Småland coastal cities and Germany as well as for the local trade