The next job was to fit the top cant rails at each side and front/back, so that the roof bearers could be fitted. Once that was done, we could fit the roof sheet. In practice, this was a big job, as the cant rails needed to be stuck in place with the corner castings as well, so it was a once-only job, we wouldn't get a second chance at it. In practice it went OK, the extrusion slots had to be primed with adhesive and then lifted up into place over the side panels, after which the corner casting caps could be fitted. It sounds fairly easy, but we had a couple of trial assemblies to make sure we had it right.