The prior assembly is still lying front side down on the ground. The roof joists are sticking straight up in the air. Mark a line parallel to the end of the roof joist. The height of the parallelogram should correspond to the amount of the overhang shown in F12. This is shown in the photo on the upper left. (In the photo you can see the two roof joists. The front of the frame is below on the ground and extends to the left.)
Next drill a bolt hole trough each roof joist and its corresponding back wall upright. The photo on the upper right shows how to use a clamp to hold back wall piece up in the air while drilling. Note the back wall piece is flush with what will be the top of the roof joist. It also follows along the line drawn in the previous step to provide some overhang.
After drilling, remove clamps and assemble the back wall. The back wall frame consists of a base that will sit on the concrete blocks (cell D11) and two uprights which are square on one side and lengths (C14 and D14) on the other. Screw them together as shown on the upper left. The longer side of the uprights are on the same side. Shown here.
Take the assembled back wall and line it up so the corresponding bolt holes are near each other, the connect them with the bolts, washers and nuts. But do not tighten. The back wall should be able to swing freely
