I has already attached the castors prior to assembly (we assembled it upside down and flipped it). We rolled the frame outside and lifted it onto the wall frame of the observatory.
I was relieved to find it fitted well and rolled easily. The next step was to install the anchor mechanisms (four of them). As you can see from the picture below, I went for "cheap and cheerful!"
These latches, one on each corner, can be tightened by screwing the barrel. On each side, they angle away from each other so that the roof is anchored no matter the wind direction. Nathan and I pushed as hard as we could and the frame was as solid as if we had nailed it in place. The next step was to erect the gables on the frame:
And finally, we added the roof braces:
Problem! We cut the roof frame exactly to size, but the braces were actually longer than the shed by an inch or so! As the shed is also exact dimensions, we were a little perplexed. Our plan to fix the issue is quite simple. I am going to add weatherboards to all sides, so I will just add a 2 x 4 to the back and a 2 x 8 to the front. These boards will "hang down" off the roof frame and keep out the weather. Once they are attached, we'll simple move the gable bases out an inch or so until the whole assembly is square.
Work finished, we covered the building in a tarp. Next week, we should be able to get the roof on....