Twenty-two pairs of internal frames, also made of oak, were arranged head to tail to give almost vertical sides. All the pairs consisted of two timbers, each made of a single naturally bent timber which was cut from a tree junction (main trunk as floor support, and branch junction as side support). In every case, frames were always installed in pairs covering the whole length of the bottom, but alternatively supporting only one side of the hull. The only exception is a sixth pair, which was a single piece of oak with a mortise cut in the center to function as a mast-step. The framing was fastened to the planks with some 300 iron nails driven from inside. They passed first through the frame, and then the strakes. Any projecting end was clenched at the right angle (double-clenched according