Rust

Thanks for the reply. I have the corner sections from a donor car its under the corner and inside the car that im trying to figure out. I suppose i can remove the cowl all the way accross up to the wipers. I can then get to the bottom part. I can cut out the rust on the underside that leads into the heater box and patch it, (going to be a pain)i just need to know how the rain water drains out.