I have to replace a small section (about 20 tiles /5 courses) of plain concrete tiles..They have two holes at the top of them and are nailed into the battens...My question is when I have gone up the courses how on earth to I nail the final course as I will be unable to get access to the nail holes because the course on top will prevent access...I ought to add these are large concrete Fortecrete tiles...Any ideas please folks...I'm a bit of a beginner to this but it has got me baffled!