UL 437

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UL 437

UL 437 is a security rating from Underwriters Laboratories that provides a barometer for the security of a keyed lock. Included are door locks, locking cylinders, security container key locks, and two-key locks. Though many manufacturers reference it as such, UL 437 does not define the standards for a "high security lock" in the United States. It is, however, referenced by high security standards, such as BHMA/ANSI 156.30.


1. A product refers to any type of lock or component defined within the standard.

2. A door lock is a rim or mortise locking assembly that is used on doors to deter unauthorized opening by one or more of the following methods:

  • Bypass
  • Lockpicking
  • Impressioning
  • Destructive Entry (specifically: punching, sawing, drilling, pulling, and other methods using small hand tools)

3. A locking cylinder is a key cylinder that is used within door locks, alarm control and shunt switches, utility locks, and similar devices to resist unauthorized opening by one or more of the following methods:

  • Lockpicking
  • Impressioning
  • Destructive Entry (specifically: "forcing methods", drilling, and pulling)

4. A security container key lock is a lock designed for use on key-locked safes, collection safes, and similar security containers to resist unauthorized opening by one or more of the following methods:

  • Lockpicking
  • Impressioning
  • Destructive Entry (specifically: "forcing methods", punching, drilling, and pulling)

General Construction and Operating Requirements

  • The product shall be constructed so that it may be readily and conveniently operated when the proper key or keys are used.
  • The lock must be practicable for installation by a trained locksmith and able to be installed in a position or location that does not degrade its burglary-resistant qualities.
  • Parts must maintain a high degree of tolerance and uniformity. This is especially important with regard to bittings.
  • Locks must be constructed of brass, bronze, stainless steel, or an equivalent corrosion resistant material. Alternatively, locks shall have a protective finish that meets salt-spray tests.

Lock Requirements


  • Door locks and cylinders must provide at least 1000 key differs. Security containers must provide at least 1,000,000 differs. Two-key locks must provide at least 64 guard key differs and at least 15,000 customer key differs.

Security Container Key Locks

  • Keys shall be field changeable.
    • The bolt lever must fit snugly on its post and shall be secured tightly.
    • The wheels, tumblers, levers, or pins must be at right angles to their mounting post.
  • In a combination lock:
    • The fence face shall be perpendicular to the plane of the tumblers.
    • Clearance between the fence face and the tumbler wheels shall not be less that 0.025" (0.64 mm) when the bolt lever is raised by means of a driver cam, and not less than 0.015" (0.38 mm) when the bolt lever is raised by means other than the driver cam.
  • Mechanical means must be provided that immobilize the bolt if the lock is punched or pulled.
  • The tolerance between plug and shell in a pin-tumbler lock must be less than one cut depth.

Endurance Tests

  • The lock must function properly during 10,000 complete cycles of operation at a rate not exceeding 50 cycles per minute.
  • A lock with a field-changeable key or removable core design must function properly after 50 changes of the core or key.

Attack Resistance Tests


  • Tools used include common hand tools, hand or portable electric tools, drills, saw blades, puller mechanisms, and picking tools. For door locks only, pry bars up to three feet (0.9 m) are also used.
  • Tools used for two-key locks must not include saws, puller mechanisms, or portable electric drills.
  • Common hand tools are defined as chisels, screwdrivers no more than 15" (380 mm) long, hammers having three pound (1.36 kg) head weight, jaw-gripping wrenches, and pliers.
  • Puller devices are to be either a slam-hammer mechanism, having a maximum head weight of three pounts (1.36 kg) or a screw type.
  • Picking tools are common or standard patterns, as well as those designed for use on a particular make or design of cylinder.
  • Portable electric tools are identified as high-speed handheld drills that meet the following criteria:
    • Maximum operating speed of 1900 RPM
    • Maximum 0.25" (6.4 mm) chuck size
    • Use high-speed drill bits
    • Use electrically operated vibrating needles

Test time for attack resistance

Times are listed in minutes and vary based on the type of attack and the type of lock.

Test Door Locks/Cylinders Security Container Key Locks Two-Key Locks
Picking 10 30 45
Impressioning 10 30 45
Forcing 05 30 05
Drilling 05 30 n/a
Sawing 05 30 n/a
Prying 05 30 n/a
Pulling 05 30 n/a
Punching 05 30 n/a

Test methods

Locks are subjected to the following eight tests[1]:

UL 437 rated locks

See Category:UL 437 locks


See also