A typical family tipi is a conical, portable structure with two adjustable smoke flaps, multiple poles (historically from 12 to 25 feet long) called lodge poles.[note 5] Lodgepole pine is the preferred wood in the Northern and Central Plains and red cedar in the Southern Plains.[22] Tipis have a detachable cover over the structure. The cover historically used buffalo skins; an optional skin/cloth lining; and a canvas or bison calf skin (historically) door. There may also be an optional, partial interior ceiling, called an ozan in Lakota, that covers sleepers and protects them from rain.[23][24][note 6]
Ropes (historically raw hide) and wooden pegs are required to bind the poles, close the cover, attach the lining and door, and anchor the resulting structure to the ground. Tipis are distinguished from other tents by two crucial innovations: the opening at the top and the smoke flaps, which allow the dweller to cook and heat themselves with an open fire, and the lining that is primarily used in the winter, which insulates while providing a source of fresh air to fire and dwellers. Tipis were designed to be easily set up or taken down to allow camps to be moved to follow game migrations, especially the bison. When dismantled the tipi poles were used to construct a dog- or later horse-pulled travois on which additional poles and tipi cover were placed.[1]
Tipi covers are made by sewing together strips of canvas or tanned bison hide (historically) and cutting out a semicircular shape from the resulting surface. Trimming this shape yields a door and the smoke flaps that allow the dwellers to control the chimney effect to expel smoke from their fires. Old style traditional linings were hides, blankets, and rectangular pieces of cloth hanging about four to five feet above the ground tied to the poles or a rope. Today's modern lining is the most difficult element to measure, since it consists of trapezoid-shaped strips of canvas assembled to form the shape of a truncated cone. The poles, made of peeled, polished and dried tapering saplings (historically pine), are cut to measure about six feet more than the radius of the cover.