When we first put the OSB boards onto the trusses, we made the seemingly reasonable assumption that you simply started nailing from the bottom, which we did.

At this point we met Robert who did a good job at not laughing at us whilst explaining how we had to rip it all off and start again. Properly. In true Canadian spirit (or perhaps just out of pity), he then preceded to turn up with his tool belt and hammer to help us do it.