Cherokee summer houses were rectangular warm-weather residences built with vertical posts supporting a gabled roof covered with bark slabs or grass thatch. Their walls could be fully enclosed with wattle and daub or only partly covered, and some had open gable ends that served as smoke holes. Cane and saplings were woven through the upright posts and daubed with clay to form the covered walls. Some reached 60-70 feet in length and may have included a second story, though location and terrain influenced their size, with smaller houses more common in narrow, flood-prone mountain river valleys. Cooking was likely done both inside and outside, depending on the weather, and Cherokee women made and tended the fires and gathered the wood. Corn cribs were another documented Cherokee village and homestead structure in the 18th century, raised on posts several feet above the ground with floors of round poles so corn worms would fall through and the corn would be protected from weevils. They also served as elevated storehouses for corn, beans, dried pumpkins, and other provisions, accessible by ladder and found at every Cherokee homestead. Dugout canoes, used for thousands of years, were one of the Cherokee's principal means of transportation before European contact. They were made from large trees, usually poplar or white pine, by controlled burning and stone tools, with mud and straw protecting the trunk above the base fire, the charred wood chipped away as the tree was felled, and the center then burned and hollowed out in a process that could take up to six months for a large canoe. Cracks were patched and the wood waterproofed with heated pine pitch, ground charcoal, and bear fat. Canoes used on major rivers such as the Tennessee and French Broad were 30 to 40 feet long and could carry 12 to 20 people, while shorter canoes were built for smaller streams such as the Hiwassee. Trade with Europeans brought metal tools such as adzes and axes, which greatly reduced construction time, and at least two 18th century Cherokee canoes survive today.