Floors were usually of hardened clay, but in a few cases they were paved with stone slabs. A basinlike fire pit with a raised rim lay near the center of the floor. Extending from the south side of the pit to the walls there were often ridges of mud. These were later replaced, in some areas, by partitions, sometimes several feet high, made of slabs or adobe. Metates are commonly found in the southern section, and it has been suggested that this may have been the women’s part of the house. A short distance on the other side of the fire pit is a small hole, known as the Sipapu. Similarly placed holes in present day ceremonial structures of the Pueblo Indians represent the mythical place of emergence from the underworld from which the first people came to the earth. The partitioning of the Modified-Basketmaker houses may have served to segregate religious from secular activities. It is believed that originally each house had its own shrine. In later times highly specialized structures were built for ceremonial practices. This is foreshadowed in the Modified-Basketmaker period for one site belonging to this horizon has been found which contained a larger structure, similar to the houses, but apparently not used as a dwelling place.[105] Toward the end of the period in some areas, particularly in Southwestern Colorado, some surface houses were built which presaged the type of structure found in the next period. Villages have been excavated in which separate pit houses were still used for living quarters, but there were also some dwellings which were above ground and had contiguous rooms.[83][95] Another important development in this period was the manufacture of true pottery. Some unfired forms were still made. Sometimes they were molded in baskets and in other cases they were started in baskets and finished by a coiling technique. To produce a vessel by this method, a thin rope of clay is formed, then wound around in a circle with each row or coil being attached to the one preceding it. Each added ring adds to the height of the vessel wall. If a smooth surface is desired, the depressions which mark the joining of the coils are obliterated. The Anasazi achieved this by scraping with a thin gourd or wooden implement, or sometimes with a piece of broken pottery. The principle of the potter’s wheel was never discovered in the Southwest. At one time it was felt that pottery making might have been a local development of the Modified Basketmakers, but this theory has been largely abandoned although it has not really been disproven. The belief most generally held is that knowledge of pottery manufacture, as well as maize, originally spread from Middle America to the Southwest by diffusion. Some archaeologists now believe that the Modified Basketmakers may have learned about pottery from people living in southwestern New Mexico who were making pottery at an earlier date.