With a very high humidity level and heat to go with it I decided that I would take my time on the project tonight. So I started in the shop by fabricating the corner boards. I cut a rabbet joint along the entire length of each 2-1/4" strip of wood. Then I nailed a 1-7/8" inch strip in the joint with polyurethance glue applied to both surfaces of the joint. This glue has a unique property, as it starts to cure it produces a foam that oozes from the joints. This can be cleaned up with a chisel later. I got all four constructed and installed on the shed. I also installed a 3/4" X 7/8" strip of rough sawn cedar along the joint between the siding and the sofit, covering the gaps left by less than perfect cuts.