#tumbler.obstructor  a movable obstruction in a lock that must be adjusted to a given position (as by a key) before the bolt can be thrown
  supertype:  #obstructor__obstruction__obstructer__impediment__impedimenta  any structure that makes progress difficult
  part of:  #lock.holdfast
  subtype:  #lever_tumbler__levertumbler__lever  a flat metal tumbler in a lever lock
  subtype:  #pin.tumbler  cylindrical tumblers consisting of two parts that are held in place by springs; when they are aligned with a key the bolt can be thrown

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