The frames are oak and fastened with treenails. In many early ships treenails (trenails, trunnels) were used to fasten large timbers. Next, the rest of the framing was added, joined with straight nails and treenails. Where suitable metal was not available, it was possible to use treenails (pronounced trennels). In later corvettes the ratio was changed to two treenails to one bolt. The planks are all fixed by treenails ("pasak") into the bulkheads. Ancient shipbuilding used treenails to bind the boat together. Treenails were extensively used constructing railroads in North England. Treenails are typically in diameter and are hand whittled with rough facets. Fastenings were originally treenails, but were replaced during restoration by spiking. In addition, treenails have the ability to move over time and retain structural integrity.