Types of Locks


  • A lock having a latch bolt or a dead bolt operated by a key or a thumbturn or both. This lock is often used in addition to another lock, which may or may not be key operated but which has a latch bolt operated by knobs or levers.
  • Bored Dead Latch
  • (Also called tubular or cylindrical dead latch) A lock fitting round bored openings in the face and edge of a door and having a dead latch operated by a key or thumbturn or both.

  • Bored Dead Lack
  • (Also called cylindrical or tubular) These are locks or latches fitting round bored openings in the face and edge of a door. If they are key operated, the cylinder is contained in the knob and so occasionally one hears them referred to as "key-in-the-knob-locks." This is imprecise as other types of locks also have cylinders contained in the knobs. The round hole in the face of the door is usually 2 1/8 inches in diameter and the hole in the edge of the door is 7/8 inch to 1 inch. When the lock is installed, the face hole contains the lock body and the edge hole contains the latch bolt.

  • Double Cylinder Dead Bolt
  • Any type of auxiliary lock requiring a key to project or retract the dead bolt (lock or unlock) from either side.

  • Interconnected Lock
  • (Also known by a number of different trade names) A lock having a separate latch and dead bolt mechanically interconnected and installed in round bored openings in the face and edge of a door. It is best known for providing dead bolt security with the life safety feature of simultaneous retraction. When the dead bolt is projected, a single turn of the inside knob retracts both the dead bolt and the latch bolt. This simultaneous retraction function is also available with some functions of mortise locks.

  • Mortise Dead Latch
  • An auxiliary lock fitting a cavity prepared in the edge of the door and having a dead latch operated by a key or thumbturn both. The key or thumbturn engages the lock through holes prepared in the faces of the door.

  • Mortise Dead Lock.
  • An auxiliary lock having a deadbolt instead of a dead latch and otherwise the same as a mortise dead latch.

  • Mortise Lock
  • A lock fitting a rectangular shaped cavity in the edge of a door. A round hole in the face of the door receives a spindle to which knobs or levers are attached. If key operated, a second round hole above the first receives the cylinder(s) and thumbturn. Some functions use two cylinders which is not a violation of the codes because the inside knob always operates. Some functions use two cylinders which sometimes is a violation of codes because the inside key projects a dead bolt or locks the inside knob which can only be unlocked by key. (This example of key operation on the inside applies equally to other types of locks and is mentioned under mortise locks only because it originated with them.)

  • Backset
  • The distance from the edge of the door to the centerline of the cylinder at the centerline of the door thickness.

  • Auxiliary Dead Latch
  • A plunger which, when actuated, automatically locks a projected latch bolt against return by end pressure.

  • Dead Bolt
  • A lock component having an end which protrudes from or is withdrawn into, the lock front by action of the lock mechanism. When the door is closed and the dead bolt thrown, it extends into a hole provided in the strike thus locking the door. It does not retract with end pressure.

  • Latch Bolt
  • A lock component having a beveled end which projects from the lock front in an extended position, but may be forced back into the lock case by end pressure or drawn back by action of the lock mechanism. When the door is closed, the latch bolt projects into a hole provided in the strike thus holding the door in a closed position.

  • Deadlocking Latch Bolt
  • A spring actuated latch bolt with a beveled end and incorporating a plunger which, when depressed, automatically locks the projected latch bolt against return by end pressure. Also called dead latch.

  • Cam
  • In this publication, a component fastened to the back of a mortise cylinder plug or mortise cylinder thumbturn. When rotated, it engages the lock mechanism and either locks or unlocks.

  • Case
  • The housing of a lock.

  • Cylinder
  • The cylindrical subassembly of a lock containing a cylinder plug with keyway and a cylinder body with tumbler mechanisms.

  • Cylinder Body
  • The portion of a cylinder that surrounds the plug and contains the tumbler mechanism.

  • Cylinder Plug
  • A tubular portion of the cylinder which rotates within the cylinder body when the correct key is inserted into it and turned.

  • Cylinder Guard
  • Material that surrounds the otherwise exposed portion of a cylinder to protect the cylinder from wrenching, cutting, pulling, or prying.

  • Cylinder Housing
  • The portion of a lock that surrounds and retains the cylinder body. It can be a knob, part of the lock case or other anchoring means.

  • Lock Front
  • A plate fastened to the edge of a door through which the bolts pass.

  • Recessed Cylinder
  • A cylinder where the cylinder head is flush with, or recessed below, the outside surface of the trim to protect the cylinder from wrenching, cutting, pulling or prying.

  • Strike
  • A plate fastened to the door frame or the inactive leaf of a pair of doors into which the bolts project.

  • Armored Strike
  • A strike reinforced in such a way as to strengthen the frame to which it is applied.

  • Strike Box
  • A housing used in back of a strike to enclose the bolt openings.

  • Tailpiece
  • A bar projecting from the back of a rim or bored lock cylinder engaging the lock mechanism and when rotated by the key or thumbturn either locks or unlocks.

  • Thumbturn
  • The component that projects or retracts a dead bolt or latch bolt by grasping with the thumb and fingers and turning. Sometimes called a turnpiece or turn.

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