Each frame piece is treated with boiling water and then bent, over the knee or around a tree, to a slightly greater degree than is needed. While thus bent, each pair is wrapped lengthwise over the end with a strip of basswood or cedar bark to hold the ribs in shape. Sometimes a strut is placed under the bark strips to maintain the desired form, or a cross-tie of bark may be employed. The ribs are then allowed to season in this position. Another method, which will be illustrated later (p. 53), involves placing ribs of green spruce in their approximate position and forcing them against the bark. In this method, a number of long battens are placed over the roughly bent ribs laid loosely inside the bark cover, and are spread by forcing a series of short crosspieces, or stays, between them athwartships. The bark is given a good wetting with boiling water to make it flexible and elastic, so that the pressure applied to the battens by the temporary crosspieces brings the bark to the shape desired for the canoe. The rough lengths of the ribs are determined by use of a measuring stick or by measurements made around the bark with a piece of flexible root or a batten of basket ash. The ribs, in any case, are made somewhat longer than required to allow a final fitting when being placed over the sheathing. It can be seen that the exact form the canoe takes is largely a matter of judgment and of the flexibility and elasticity of the bark, rather than of precise molding on a predetermined model, or lines. [Illustration: Figure 44 DETAILS OF RIBS and method of shaping them in pairs in a bark strap or thong so that they take a "set" while drying out.] In the Malecite canoe the ribs are wide amidships, 3 or 4 inches, and narrow to 2½ or 2 inches toward the ends. The thickness is an even ⅜ inch. Most birch-bark canoes have ribs of even thickness their full length, but in a few the thickness is tapered slightly above the turn of the bilge, usually when the tumble-home is high on the sides and rather great. The width, as previously explained, is usually carried all across the bottom; above the bilges there is a moderate taper.