Finishing, and the top ridge
At the top end of each ridge, make a cut across the fold at 1cm (3/8") down from the end as shown.Now cut off the folded bit as far as the first cut, so you have removed the ridge part. Make sure that it lies flat when opened out. Repeat for each ridge.
And now the part where I don't have photos of the process - I didn't think to take them while I did the original roof! I was too busy trying to get it right to be bothered with the camera as well :)
Make sure your pieces are cut straight and square. Leave extra at the back as the sheet is hard to measure accurately with the folds making themselves known :)
Spread tacky glue onto the roof surface and spread evenly. Start laying the painted sheet from the front to the back (it may help to have a friend hold it up from the glue as you work your way across). Smooth it down along the 'valleys' (I used a soft cloth), and also push into the ridges with a ruler (not a metal one, it may chip the paint) to make sure they sit down neat and crisp.
It also helps to squeeze the ridges down at each end with a pair of tweezers as the glue dries. The ridges will try to rise up a little, and as the glue gets more tacky may need help to be pushed down.
When it's dry, trim the back edge. I left 1cm extra and folded it down onto the back of the house.
Take your extra piece of painted card, and cut it 3cm wide along the length, and mark the centre line. Pre-fold this, then run a line of glue along the centre line. Lay a length of fine dowel along this. The dowel I used was the same diameter as toothpicks (you could use these instead, after cutting off the points).
Let the glue dry.
Glue this piece and lay on the roof with the edges meeting the folded ridge ends.
The dowel lies along the top edge. Press gently with your fingers along and around the dowel to delineate it a little. Trim the ends.
And here's your roof!