3M56 Mk2


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 perimeter doors and main access routes.


The 3M56 Mark 3 is a mortice hookbolt 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.

Secure locking is achieved as follows:

Servant Key. Operates first throw only.
Locking is achieved by inserting the servant key into the dished keyhole and rotating fully in a clockwise direction, this action will extend the anchor bolt to expand the reinforced hooks to their fully thrown position.
Unlocking is achieved by inserting the servant key into the dished keyhole and rotating fully in an anti-clockwise direction, this action will withdraw the anchor bolt and retract the reinforced hooks to their rest position.

Note: the Servant key will not operate the second (master) throw.

Master Key – Operates second throw only.
Locking, by inserting the master key into the offset keyhole and rotating clockwise the anchor bolt can be thrown to its second position, preventing the servant key operating the lock.
Note: the use of the master key does not engage the hooks any further.
Unlocking is achieved by inserting the master key into the offset keyhole and rotating once in an anti-clockwise direction. This action will withdraw the anchor bolt to its first position to enable operation under servant key.
Note the Master key will not operate servant throw.


Laminated and hardened hooks to resist cutting.
Reinforcing bolts to resist forced attack.
16 lever highly durable mechanism.
Independent Servant and Master actions. 
Low friction key journals.
Lever arrangement designed to provide extended product life.
Dedicated key profiles operates Mark 1&2 group of locks only.
Escutcheon designed to give positive key alignment.
Security fixings to prevent unauthorised removal.


Lock tested to a minimum of 500,000 key operations. 


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 2 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.
Servant key action only, version available on request.
Master key action only, version available on request.

Materials and finishes

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.

Dimensions and Weights

Lockcase Depth 171.5mm
Lockcase Length 14.3mm
Lockcase Width 21.0mm

Weight (lock only) 3.0Kg

Total Range

The lock is available in left or right hand variants for opening in or opening out doors and can be fitted to steel or wooden doors. For applications requiring cell side furniture a range of options are available on request.

Lock is suitable for use on all door types, however on steel doors the short forend version should be ordered and for wooden doors the long forend version is recommended.

Fully dimensioned customer drawings are available on request to assist with door preparation.