To make the frame for the underground hall or passageway, first nail Q, S across the door-jambs, to form the top to the doorway, after which put in the supports Q, R and S, T. Next build the frame U, V, X, W, and join it to Q, S by the two pieces, Q, U and S, V, and put in the middle frame-support marked Z, Z, Z, Z. [Illustration: FIG. 77.--The Frame.] The passageway should be about six feet long, and the front doorway (U, V, X, W, Fig. 80) of just sufficient size to enable you to creep through with comfort. The bottom-piece, W, X, can be nailed to a couple of stakes driven in the ground for that purpose. The next thing in order is the floor, and to make this firm you must lay a number of two-by-fours, parallel to B, D and F, H and see that they are level. You will need a number of shorter pieces of the same material, to run parallel to F, H and W, X for the hall floor, as may be seen in Fig. 79. Across these nail your floor securely, as shown in Fig. 79. There Are No Windows to the underground house, and but two openings: one in the roof for the ventilator, and the doorway, Q, S, L, J, Fig. 77. Since the outside of the wall of this sort of a house is hidden by earth, it is not necessary to remove the diagonal braces upon the ends or sides, but the inside should be neatly finished, and the four sides must be boarded up from the inside, after which the side-walls to the passageway may be nailed on from the outside, the boards running from the floor to the string-pieces, Q, U and S, V, as shown in Fig. 79. When this is finished, roof the house, laying the boards parallel with A, E and C, G, and allowing them to project front and rear and overlap at the sides. Over each crack in the roof nail another plank, as shown in Fig. 79. The Roof may be made without the overlapping boards and the cracks covered with strips of tar-paper or old oil-cloth, or the roof may be preserved and the cracks filled by treating the whole to a coating of hot tar, daubed on with a brush made from rags tied to the end of a stick. Any sort of roof which will keep out the rain will answer the purpose. Gumption. The plans given may be, and are expected to be, altered to suit requirements. If you use this roofing you must use substantial supports, in the way of rafters, and put them close together. In all cases, use your common-sense. Don’t put much earth on a frail roof; it is only necessary to cover the boards with sufficient earth or sod to conceal the wood. Make a long box, of four boards (Fig. 82), for A Ventilator,