Here's how to restore the missing brass hardware on an antique door. The ghost image of original brass hardware is often visible. It can be replicated by tracing the impression. A cardboard template is made to scribe the design. The brass is cut on a bandsaw and smoothed with a belt sander. The piece is polished and installed on the door.
If you find irregular surfaces at the glue line in wood projects, the problem can be moisture levels. This can happen, for example, when one piece has a 15% moisture content, while those next to it are at 8%. If you glue and plane boards with unequal moisture, those with higher moisture will eventually shrink more than those with less moisture.