3M56 Mark 3 - Morticed Hookbolt Lock – Single Action



To provide secure deadlocking of sliding doors or gates where an enhanced level of security is necessary. This lock is specifically designed for very high use applications; typically securing internal doors and main access routes.


The 3M56 Mark 3 is a mortice hook bolt lock of robust construction based on the Chubb Locks Custodial Services small mortice footprint. Twin locking laminated and hardened hooks are used to provide positive engagement in the frame with maximum strength.

The lock provides deadlocking operated by a unique key profile to the Mark 3 range of locks and will not operate Mark 1 or Mark 2 lock variants.

The lock is operable from both sides and the escutcheon is designed to allow only the correct key profile being inserted into the lock.

The lock cannot be Master Keyed.

Secure locking is achieved by:

  • Locking is achieved by inserting the key into the dished keyhole and rotating fully, this action will extend the anchor bolt to expand the reinforced hooks to their fully thrown position.
  • Unlocking is achieved by inserting the key into the dished keyhole and rotating fully, this action will withdraw the anchor bolt and retract the reinforced hooks to their rest position.



  • Laminated and hardened hooks to resist cutting.
  • Reinforcing bolts to resist forced attack.
  • 12 lever highly durable mechanism.
  • Low friction key journals.
  • Lever arrangement designed to provide extended product life.
  • Dedicated key profiles.
  • Escutcheon designed to give positive key alignment.
  • Security fixings to prevent unauthorised removal.


  • Lock tested to a minimum of 500,000 key operations.
  • Saw attack 10minutes
  • End load 13.5 kN
  • Pull test load 13.5 kN

Additional Features

  • Suitable for external and internal use.
  • Specially designed forend and fascia locking plates.
  • Available in alternative furniture finishes on request.
  • Can be keyed with 3G112 Mark 3 Deadbolt
  • Gate boxes for steel door applications recommended.
  • Escutcheon trim plates supplied for wooden door variants as standard.
  • Monitored versions available with micro-switch sensing of bolt position.
  • Single sided version available on request.

Total Range

  • The lock is not handed, however for use on steel doors the short forend version should be ordered and for wooden doors the long forend version is recommended.
  • NOTE: CLCS recommend this lock is used in conjunction with a wooden door 54mm thick. Please contact CLCS for guidance if alternative wooden door thicknesses are required.
  • Fully dimensioned customer drawings are available on request to assist with door preparation.

Dimensions & Weights

Lockcase depth (total) 171.5mm
Lockcase height 141.2mm
Lockcase width 21mm
Weight (lock only) 3kg



  • Lock case - carbon steel electro-plated.
  • Anchor bolt - stainless steel and carbon steel composite.
  • Hook bolts - hardened steel.
  • Escutcheons - silica brass
  • Keys - hardened steel
  • Levers and springs - brass / phosphor bronze