Just got the back plates of the guitar thicknessed (yes, that is a real word - at least one that guitar makers use) and glued together. This was the first time that I have had a really critical seam to glue together and match up. It was not easy, but it was a very rewarding experience.

First, I thinned the two back halves down to their rough dimensions (2.8mm) with the safety planer that I used for the sides.

Then using a plane and sandpaper, I had to create a perfect edge on both plates to join them. This back seam is a critical seam as it will be under some pressure and so the connection for the two halves needs to be near perfect.

This whole operation is done on a shooting board which is just two 36" long pieces of 3/4 MDF - one 16 inches wide, the other 10 inches wide - screwed together to create a straight and elevated work board. I piece of 1" pine scrap is screwed to one end as a back stop to set the plates against as you are working them.

Because I get obsessed about these things, it took me about 2 hours to get the seam right. I started by removing high or low spots with my block plane (the small plane) then working both plates with my longer #5 plane to create a straight edge. In the end, I found that it was much easier to perfect the seam with a piece of 220 sandpaper against the bottom of the plane. This process is hard to explain and if you are interested here is video that shows the process:

I have found Robert O'Brien's videos to be a great help in this project by the way. He has a ton of good information and training available.

I used a method for joining what some call the nail and batten technique. Once the back plates were glued up and lined up I applied some weights to the seam and let it set for about 3 hours.

After letting the whole thing sit for about 14 hours, I finished it up with some leveling and scraping.

The back is looking nice. Now to cut it to its rough shape and brace it.