It will be noticed that these doorways all conform to one general plan and that this plan required an opening considerably larger in its upper third than in the lower two-thirds of its height. This requirement seems to be the counterpart or analogue of the notched doorway, which is the standard type in the cliff ruins of Canyon de Chelly and other regions, and still very common in Tusayan (Moki). Figure 304 shows a notched doorway in Canyon de Chelly and figure 305 gives an example of the same type of opening in Tusayan. The object of this peculiar shape in the regions mentioned has been well established,[9] and there is no reason to suppose that similar conditions and a similar object would not produce a similar result here. This type of opening had its origin in the time when the pueblo builders had no means, other than blankets, of temporarily closing door openings and when all the supplies of the village were brought in on the backs of the inhabitants. In order to secure protection against cold and storm the opening was made of the smallest possible size consistent with its use, and the upper part of the opening was made larger in order to permit the introduction of back loads of faggots and other necessaries. This purpose would be almost as well served by the openings of the cavate lodges as by the notched doorway, and at the same time the smallest possible opening was exposed to the weather. The two types of openings seem simply to be two different methods of accomplishing the same purpose--one in solid rock, the other in masonry. That it was considered desirable to reduce the openings as much as possible is evident from the employment of framing slabs in the lower portions, reducing the width of that part generally to less than a foot, while the upper portions are usually 3 feet and more in width, and the absence of framing slabs in the upper part of the openings was probably due to their use as suggested; no slabs could be attached with sufficient firmness to resist the drag of a back load of wood, for example, forced between them. The strict confinement of door openings to one type suggests a short, rather than a long, occupancy of the site under discussion, a suggestion which is borne out by other details; and this unity of design renders it difficult to form a conclusion as to the relative age of the two types of openings under discussion. So far as the evidence goes, however, it supports the conclusion that the doorways of the cavate lodges were derived from a type previously developed, and that the idea has been modified and to some extent adapted to a different environment; for if the idea had been developed in the cavate lodges there would be a much greater number of variations than we find in fact. There can be no doubt, however, that the cavate lodge doorways represent an earlier type in development, if not in time, than the notched doorways of Tusayan.