Windscreen frame repairs - example by photos

These stages show reconstructing a rotten ash windscreen sill from a Barker -

Note that if replacing the wood under the screen it is best if the corners of the steel are rusted - because the 8 screws that retain it to the bulkhead face outwards and so cannot be removed with the steelwork in-situ.
The other thing that makes this job awkward is removing the panel pins that attach the steel rim of the windscreen surround to the ash member.

The new piece of ash visible behind the steelwork. It is prudent to treat with a preservative to prevent future decay.

The steel patches are welded to the car and cut with a 1mm thick cutting disc to ensure patches can be made without leaving gaps or needing work to shape them up.

The patches are then lead-loaded and the repair re-painted.