3G112 Mk3


To provide secure deadlocking of swinging doors or gates. This lock is specifically designed for very high use applications; typically securing internal doors and main access routes.


The 3G112 Mark 3 is a mortice deadlock of robust construction based on the Chubb Locks Custodial Services small mortice footprint. The mechanical deadbolt provides a throw of 19mm.

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 to be inserted into the lock.

Secure locking is achieved as follows:

Pass Key.Locking is achieved by inserting the key into the dished keyhole and rotating fully in a clockwise direction, this action will fully extend the bolt.
Unlocking is achieved by inserting the key into the dished keyhole and rotating fully in an anti-clockwise direction, this action will fully withdraw the bolt.


Composite deadbolt, with carbide anti-cutting rollers and 19mm throw.
12 lever highly durable mechanism.
Low friction key journals.
Lever arrangement designed to provide extended product life.
Dedicated key profiles operates Mark 3 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.
Saw attack 12 hours.
End load 9 KN.
Side Load 13.5 KN. 

Additional features

Suitable for external and internal use.
Range of fixings including reinforcing plates and locking plates.
Available in alternative furniture finishes on request.
Can be keyed with 3M56 Mark 3 Hook Bolt.
Lock interchangeable with 3G317.
Gate boxes for steel door applications recommended.
Escutcheon trim plates supplied for wooden door variants as standard.
Rebate kit available for wooden door applications.
Monitored versions available with micro-switch sensing of bolt position.
Single sided version available on request.

Materials and finishes

Lock case - carbon steel electro-plated.
Bolt – stainless steel and brass composite.
Escutcheons – silica brass.
Keys – hardened steel.
Levers and springs – brass / phosphor bronze.

Dimensions and Weights

Lockcase Depth (total) 171.5mm
Lockcase Length 114.2mm
Lockcase Width 21.0mm

Weight (lock only) 2.1kg

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.