The small size of the ordinary pueblo doorway was perhaps due as much to the fact that there was no convenient means of closing it as it was to defensive reasons. Many primitive habitations, even quite rude ones built with no intention of defense, are characterized by small doors and windows. The planning of dwellings and the distribution of openings in such a manner as to protect and render comfortable the inhabited rooms implies a greater advance in architectural skill than these builders had achieved. The inconveniently small size of the doorways of the modern pueblos is only a survival of ancient conditions. The use of full-sized doors, admitting a man without stooping, is entirely practicable at the present day, but the conservative builders persist in adhering to the early type. The ancient position of the door, with its sill at a considerable height from the ground, is also retained. From the absence of any convenient means of rigidly closing the doors and windows, in early times external openings were restricted to the smallest practicable dimensions. The convenience of these openings was increased without altering their dimensions by elevating them to a certain height above the ground. In the ruin of Kin-tiel there is marked uniformity in the height of the openings above the ground, and such openings were likely to be quite uniform when used for similar purposes. The most common elevation of the sills of doorways was such that a man could readily step over at one stride. It will be seen that the same economy of space has effected the use of windows in this system of architecture. WINDOWS. In the pueblo system of building, doors and windows are not always clearly differentiated. Many of the openings, while used for access to the dwellings, also answer all the purposes of windows, and, both in their form and in their position in the walls, seem more fully to meet the requirements of openings for the admission of light and air than for access. We have seen in the illustrations in Chapters III and IV, openings of considerable size so located in the face of the outer wall as to unfit them for use as doorways, and others whose size is wholly inadequate, but which are still provided with the typical though diminutive single-paneled door. Many of these small openings, occurring most frequently in the back walls of house rows, have the jambs, lintels, etc., characteristic of the typical modern door. However, as the drawings above referred to indicate, there are many openings concerning the use of which there can be no doubt, as they can only provide outlook, light, and air. [Illustration: Plate XCV. Ancient floor-beams at Kin-tiel.]