Generally, you remove the faceplate on the thin side of the door... there should be 2 screws there... then you'll see 2 holes on another faceplate underneath that one, which require an allen key of the right size... if your lucky you'll see a flathead bolt that can be loosened... then put your key only partially into the deadbolt and turn it counterclockwise and it will come out into your hand... then replace it or rekey it.
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Generally, you remove the faceplate on the thin side of the door... there should be 2 screws there... then you'll see 2 holes on another faceplate underneath that one, which require an allen key of the right size... if your lucky you'll see a flathead bolt that can be loosened... then put your key only partially into the deadbolt and turn it counterclockwise and it will come out into your hand... then replace it or rekey it.