What is a key-in-knob lock?
Identify the binding pin: Use the diamond pick to gently insert it into the lock and wiggle it back and forth. This will allow the flat edges of the diamond pick to push up on the pins and lift them to the correct height. As you wiggle the pick, you should feel for the pin that is binding and requires more pressure to move.
Apply pressure: Once the binding pin is identified, apply gentle upward pressure to it with the diamond pick. Be careful not to use too much pressure or you could damage the pin or break it.
Release tension on the wrench: Release a small amount of tension on the wrench while maintaining pressure on the binding pin. This will allow the pin to set at the correct height without being pushed back down by the other pins.