The timber arches consisted of 14 layers of timber, each , held by trenails. Ribs were attached to the strakes with cords or trenails, and thwarts installed. Symmetrical ribs or frames were then lashed to the strakes or secured with trenails. In many early ships treenails (trenails, trunnels) were used to fasten large timbers. Chairs have been fixed to the sleeper using wooden spikes (trenails), screws, fang-bolts or spikes. Other trenails are tapered with the large end being longer than the mortise. Nails and trenails have not been used in this ship to secure frames to keel. Trenails are extremely economical and readily available, making them a common early building material. Unlike metal nails, trenails can not be removed (without great effort) or reused.