Rob N, here's your zero block. I tidied it up a little. It will be attached next Sunday.
Because of a transient episode of laziness, I only spent a couple of hours in the workshop today. It took me nearly all that time to fashion the following piece, being one half of the sight door sliding track. I think it's the harder of the two parts to make, so other one shouldn't be so painfully time consuming. Two hours of hand filing is my limit, I'm afraid. Never again.
It isn't really wider on the right hand side. It's a trick of the angle of photography.