Answer:
The materials needed were around 15 poles made from "lodgepole pines", obtained from the foothills of the Rockies or from the Black Hills, plus a cover made from the hides of buffalo cows, dressed, tanned and smoked, a number of wooden skewers and two extra, thinner poles for the smoke-flaps.
A tripod of three or four lodgepoles (depending on the particular tribe) would be tied together with rawhide or hair rope and then erected. The remaining poles would simply be rested against this framework, the cover being raised on the final pole and wrapped around the entire structure. Wooden pins or skewers were used down the overlapping front seam to secure it, leaving a gap at the bottom for the doorway.
Inside, the poles would all be moved to ensure a good, tight, stable fit; the lower edge of the tipi might be held down with large rocks, or pegged - in summer it could be rolled up to allow the breeze to blow right through.
Outside, the final two thinner poles were fitted into small "pockets" on the smoke flaps - these poles could be adjusted to open, close or change the angle of the flaps according to the wind direction.
The door might be covered with a buffalo hide, a blanket or a skin stretched on a wooden framework.
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