When cutting this frame, I was a little careless with the jigsaw, and the angle of the blade wandered. At one end the cut was perpendicular to the face, at the other, the bevel was almost 15 degrees off square.
Since this piece will be supporting weight from above, and will be under compression, and will have some nice bronze screws through it holding it all together, I reckon shimming is the way to go.
A ScarySharp block plane (see previous post) makes short work of getting a really flat edge, square to the surface of the board.
The shim was cut with a circular saw with a fine cut blade (lots of teeth) and a parallel guide. Works wonders for cutting a narrow strip.
Since I'm using Balcotan PU, I can get a strong end grain to side grain glue joint. All I need is LOTS of clamping pressure.
None of my clamps were of any use in this, so I put a block of wood behind my shim, tied a cord tight around it and the notch in the far end of the frame piece (with a small piece of wood there to prevent marking) and twisted it very tight with a screw driver. This method has been in use for centuries. It's cheap and versatile.
The shim was glued in place oversize, and then I trimmed the ends to fit.
I think that this counts as a rescue.
Next I will try shimming the other frame piece that I messed up, but that will be more difficult as I want to just shim the damaged part, which means cutting a notch. The only downside of Balcotan PU, is that it's pretty intolerant of gaps.