Steps:1. The guest had a supply of old keys for his antique door latches and some hardware. You can find old-time keys at some hardware stores or shop antique stores.
2. Scrape away any old paint on the lock mechanism using the painter's tool (figure A).
3. Use a utility knife to free up the deadbolt latch. Try a variety of antique keys to find one that works (figure B).
4. If necessary to repair the mechanism, remove the screw holding one of the doorknobs on and remove the doorknob assembly (figure C).
5. Remove the screws holding the faceplate on one side of the door, then remove the screws holding the mechanism in the door and slide it out (figure D).
6. You may be able to repair the mechanism by replacing a spring, but if it's broken just find a suitable replacement of the same size. Install by reversing the steps you took in taking it out.
7. Another problem is a latch mechanism that doesn't line up with the opening in the strike plate (figure E).
8. In this case you can move the strike plate so the latch lines up. However, this will leave a cavity in the door exposed when you move the plate.
9. If the door's not too far out of alignment, use a grinding tool and power drill to grind away enough of the strike plate for the latch to fit (figure F). Always remember to wear safety glasses when working with power tools.