From G to G you may now lay the planks of your floor, if the distance is short: if not, put two poles across each side of the trees and nail them to the trunks, and two more across at each end of the pieces G, G, and nail them to G and G, and then put your flooring on parallel to the G planks. Frame, Walls, and Roof. The rest of the work is simple. To shed the rain your roof must incline one way or the other--to the front, as in Fig. 5, or to the back, as in the one-tree house, Fig. 6. Nail on an A block to each tree, and give them the same incline; then place two poles for rafters on the A blocks and nail them, each with a single nail, to the tree-trunk; this will hold them in place until you cut four straight poles for the uprights at the four corners of your house; set these up under the ends of the rafters, and nail the rafter to them and to the trees; then drive two or three nails, slantingly, in the foot of the upright to secure them to the floor (toe-nail, Fig. 92, Chap. IX.). A cross-piece on top of the front and rear completes the skeleton of your house, which may be roofed and the sides covered with boards, or only the roof made of boards with narrow strips over the cracks and the sides covered with poles, by nailing the latter to the uprights as in Fig. 5. This gives a fine rustic effect, but unless ceiled or boarded up on the inside it will allow the wind and rain to beat through. [Illustration: FIG. 6.--Frame of a One-Tree House.] If the trees are further apart than desirable, the house can be built between the trees, as in Fig. 5, but if the space is no more than required, the house can be built so that the sides enclose the tree-trunks, as the railing of the platform does in Fig. 5. A Rustic House. It is really not necessary to use any plank or boards except for the roof and floor. A boy who can handle an axe and hatchet well can make the frame, Fig. 2, from timber cut in the woods, but unless he is an expert, or can get the services of an expert axeman, he had better use plank as directed. The One-Tree House at first thought seems to be an even more serious problem than the two-tree house, but a glance at Fig. 6 will show how it can be built without much trouble.