In northern Europe, lapstrake, or overlapping, construction was developed to a high order by the 9th century ad, particularly by the Scandinavians. Lapstrake is also known as clinch-built or clinker-built construction. Planks apparently were split off a log by means of wedges, or they were hewn and assembled on the keel, one after another beginning with the garboard, the lowest. In the Viking ships and boats of the 10th century and somewhat later, lashings were still used to secure the planks to the frames. Such construction resulted in a very flexible hull, yet one of relatively great strength. The lashings eventually were replaced by through fastenings, that is, by pegs, and later were replaced by nails driven into the planking and frames.
In lapstrake construction the longitudinal seams of the planking are formed by overlapping the edges enough to allow continuous nailing. Thus, the skin, or exterior planking, adds strength to the boat. Frames are then added to give the required stiffness of form. Originally the frames were hewn of natural-crook timber, including root or limb knees and crooked trunks. Steam-bent frames became popular in the early 19th century.
This Viking ship, on display at the Viking Museum in Oslo, Norway, is an example of lapstrake construction. In Viking ships of the 9th century and later, external planks were overlapped and lashed to the ship’s frame, producing a strong, flexible hull.