Just a quick question about building a back that could be turned to shoot landscape and portrait.

I'm not so bold as to try to build one of them rotating types. My plan is to make one that can come apart be turned and then just put back in. I have a basic idea of what I'd like to do and was looking for some ideas on how I can fix the 2 bits together so it's strong and can be done relatively quickly.

My only thought so far is nuts and bolts, so industrial, fiddly, but strong.

Attached is a very crude version of what I have in the brain, so please excuse its inaccuracy, I'll just say that the board will be square and so will the bellows, so there's no need to worry about anything getting the way - so to speak.