Nicely TIG welded.

Ground smooth.

Plasma-cutting the end caps from 14-gauge cold-rolled steel from the llama project.

And the cover plate.

Here's the intermediate result.

And the final product, more or less. There's a devious finger-eating mechanism not shown, among other gruesome security measures. It's barely possible to open the deadbolt safely even from the inside, let alone through the doggy door.

Demonstrated in action.