When the key is flush, use the right tool
If the broken key is snapped off perfectly level with the front of the lock without any part sticking out to grab, you must use a proper tool designed for this. Using the wrong tool will only turn a stuck fragment into a deeply stuck fragment. The tool designed for this job is a broken-key extractor. These thin tools are meant to slide into the keyway, catch the grooves of the broken key, and pull it back out without damaging the lock. Locksmith suppliers sell dedicated extractor sets for exactly this reason, and locksmith guides recommend inserting the extractor along the cut edge of the key so it can hook the fragment instead of pushing it farther inward.
The technique matters as much as the tool. You want the lock in its neutral position, the extractor inserted carefully, and your pull to be slow and careful, rather than sudden or jerky. If the fragment starts to move, great — keep going with the same gentle pressure. If nothing happens after a few careful attempts, that is your sign to stop. The biggest mistake at this stage is turning a clean extraction problem into internal lock damage. You are trying to remove one stubborn piece of metal, not audition for a home-repair action movie.
