Step 1: Template

Make a template using cardboard or if your feeling confident draw straight onto check paper. I used one of my son's old maths book.

Step 2: Use Exterior Wood

Cut your exterior wood to size and paint with exterior paint. Leave to dry for at least 1 day.

Step 3: Test Run

I did a test run on scrap wood to make sure the holes were not too close together. It actually took me 3 tests to get it right.

Step 4: Time to Drill

Place the check paper on top of the wood and drill your holes through the paper.

Step 5: Final Step

Remove the paper and drill the screws into the ready made holes. I finished off by using a screw driver as suggested by PeterP_DIY who I got this wonderful idea from. When you use the screw driver instead of the drill you can get them nice and level.