This curious arrangement affords another illustration of the survival of ancient methods in modified forms. It is not employed, however, in closing the doors of the first terrace; these are fastened by barring from the inside, the exit being made by means of internal ladders to the terrace above, the upper doors only being fastened in the manner illustrated. In Pl. LXXIX may be seen good examples of the side hole. Fig. 75 shows a barred door. The plastering or sealing of the small side hole instead of the entire opening was brought about by the introduction of the wooden door, which in its present paneled form is of foreign introduction, but in this, as in so many other cases, some analogous feature which facilitated the adoption of the idea probably already existed. Tradition points to the early use of a small door, made of a single slab of wood, that closed the small rectangular wall niches, in which valuables, such as turquoise, shell, etc., were kept. This slab, it is said, was reduced and smoothed by rubbing with a piece of sandstone. A number of beams, rafters, and roofing planks, seen in the Chaco pueblos, were probably squared and finished in this way. The latter examples show a degree of familiarity with this treatment of wood that would enable the builders to construct such doors with ease. As yet, however, no examples of wooden doors have been seen in any of the pre-Columbian ruins. The pueblo type of paneled door is much more frequently seen in Cibola than in Tusayan, and in the latter province it does not assume the variety of treatment seen in Zuñi, nor is the work so neatly executed. The views of the modern pueblos, given in Chapters III and IV, will indicate the extent to which this feature occurs in the two groups. In the construction of a paneled door the vertical stile on one side is prolonged at the top and bottom into a rounded pivot, which works into cup-like sockets in the lintel and sill, as illustrated in Fig. 76. The hinge is thus produced in the wood itself without the aid of any external appliances. [Illustration: Fig. 76. Wooden pivot hinges of a Zuñi door.]