In 2003 two softwood beams were found in a national park in Zeeland. Both beams were full of nail-holes and imprints of large nail heads. This could be prove of a technique that was used to protect East Indiaman ships from shipworm (Teredo navalis). The technique involved applying an outer layer of (usually small) planks that were covered with wide-headed nails. These nails would eventually corrode and form a protective layer against shipworm. The beams are thus suspected to have been used as a protective layer for a ship, pier or quay. The beams are unofficially dated between the 17th and 19th century.

• Akker van den, J., M. Manders, W. van der Wens, A. Zandstra (2007).
  Bundel Maritieme Vindplaatsen 1, p. 96-97.