Okay folks, I'm interested in feedback. My current job is a set of bookcases, 14' long, 12" deep, and 36" high. They will be built in three sections and joined side by side upon installation. They will be up against a 36" high wall. Behind this wall is open space. It is the edge of a loft space, and there is a vaulted ceiling behind it, living room down below. Anyway, the bookcases will be getting a solid alder top, and the top will extend across the bookcases and the half wall. These bookcases are also in between 2 walls (at either end). So, I've got a finished top that will be 14' long, by 18 1/2" front to back. I cannot build it in a single section for several reasons. So I am making 2 sections, which will be joined together end-to-end onsite at installation. This will all be pre-finished in my shop. I need these 2 mating surfaces to join up EXACTLY flush. They also need to be scribed to the walls at either end. What kind of joint do you think I could use to accomplish this? A scarf joint is all that comes to mind. Any better ideas out there?