After the chines and floor are fitted to the keelson, the frames at the thwarts are made and set up at the desired flare and height, being held in place by temporary spreaders lashed or braced. These are sometimes stiffened by thongs from frame head to keelson at each pair, to steady the frame while the gunwale is being bent. As the lengths of the thwarts are controlled by the fairing of the gunwales, the thwarts are not fitted until after the latter are in place. As shown in the figure above, the gunwales are round poles, slightly flattened on the lower side at the headboards, where they are secured by lashings. In building, the gunwales are shaped and secured by lashing them to those side frames selected to shape the hull. The lashings that secure the side frames to both gunwale and chine are passed through holes in each member and are hove taut by means of a short lever with a hole bored in it to take the end of the lashing, which is also wrapped around the lever to give temporary purchase. The side frames have saddle notches to bear on the chine and gunwale. All lashings in the frame, it will be noted, pass through holes bored in the members and in some cases the lashings are let in, so that the sinew is flush with the surfaces of the members, to prevent the lashing from being damaged by chafing. [Illustration: Figure 168 UMIAKS NEAR CAPE PRINCE OF WALES, ALASKA, showing walrus-hide cover and lacing. Frame lashings are walrus-hide thongs. (_Photo by Henry B. Collins._)] With the gunwales faired, the remaining frames are then put in position and lashed to the gunwales and chines. An outside batten is run along each side and lashed by turns of sinew over the batten and around the side frames, with the lashings let into each member to prevent slipping and chafing. The batten is lashed at bow and stern in some umiaks, but in many it is stopped just short of coming home on the posts. Next, the short frames at bow and stern are put in place and the risers secured inside the side frames, then, with the thwarts fitted and lashed to the risers, and the ends of the gunwales are lashed together at bow and stern, the boat is ready to be covered. When ready to cover, the frame is stiffened by diagonal thong ties, each of which has one end secured by turns around the gunwale, with the other end passed through holes in the keelson and secured. These are commonly found in western umiaks; the small umiak has but one pair placed amidships. The timber used in such craft is fir, spruce, and willow, and is usually driftwood obtained at river-mouth.