A metal door lock mechanism, typically used in centre case applications for multipoint door locks, displayed against a white background.
Diagram illustrating how to measure a Mila uPVC door lock centre case gearbox, showing the "Backset" (A) and "PZ" (B) dimensions for correct fitting.
A metal door lock mechanism, typically used in centre case applications for multipoint door locks, displayed against a white background.
Diagram illustrating how to measure a Mila uPVC door lock centre case gearbox, showing the "Backset" (A) and "PZ" (B) dimensions for correct fitting.
Lockmaster

Lockmaster Hook Gearbox – Replacement Centre Case for uPVC Multipoint Door Lock – 35mm Backset 92mm PZLockmaster Hook Gearbox - 35mm Backset - 92mm PZ

£49.99 SKU: HS3720
Order by 2pm for same-day dispatch
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Same-day dispatch on orders before 2pm

The gearbox is the most common part to fail on a Lockmaster multipoint lock — replace just this centre case, not the full strip, and save.Check your backset is 35mm before ordering.

Key benefits
  • Direct Lockmaster replacement - hook or deadbolt versions
  • Restores multipoint lock function - saves replacing the full strip
  • Standard Lockmaster dimensions - measure your case before ordering
Product overview

Lockmaster Hook Replacement Gearbox

The Lockmaster hook door lock centre case gearbox is the mechanism inside your uPVC door that is operated by the handle. It is the most common part to fail when a multipoint door lock stops working properly.

Replacing the centre case is far more cost effective than buying a complete new multipoint lock. It re-attaches to your existing locking strip, saving you time and money.

Key Measurements

The most important measurements to check before ordering are 35mm Backset and 92/62mm PZ.

This gearbox is non-handed, fitting both left and right-handed doors. It supports single spindle or split spindle operation.
Delivery & Returns

How much is delivery?

UK Mainland Delivery is £2.99 on all items no matter how many you order!

Northern Ireland, Scottish Highlands, Channel Islands £6.00.

We do not offer International Delivery (Ireland, France, Spain etc).

When will my order be dispatched?

Orders before 3pm (Monday to Friday) are usually dispatched same day but may take up to 24 hours.

When will I receive my item?

We ship on 2 working day courier. Fully Tracked. Tracking will be emailed on dispatch. 

Special order items such as keyed alike locks will take longer to dispatch. Please refer to product description for lead times. 

I haven't received my item?

Please email us your name, order number and date of purchase.

We prefer email as it allows us time to research and respond.

Returns Information

We operate a 30 day refunds and return policy. 

If you change your mind you must return the product back to us within 30 days of delivery

Please include a copy of your invoice and a note stating reason for return. 

Additional keys, locks keyed alike or built to code are non refundable as they are personalised made to order goods.

Any refund, which is due to a fault or other defect, will include a refund of the applicable delivery charges otherwise not. 

It is the buyers responsibility to arrange the return of goods to us. We do not offer a collection service for returning items. 

Items must be returned including original product packaging and accessories.

We reserve the right to refuse any returns that do not comply with this policy.

Please post returns to the following address:

Home Secure (Online)

Unit 5, Brookfield Drive

Liverpool, L9 7AJ

United Kingdom

Frequently Asked Questions

The Lockmaster hook gearbox is the central mechanism in a multipoint locking system, designed to operate hook-style locking points that secure the door firmly into the frame.

Hook locks use curved locking bolts that latch into the frame, providing stronger resistance against forced entry compared to standard deadbolts.

Common signs include a stiff or loose handle, difficulty lifting the handle, or the hooks not engaging properly. These issues usually indicate internal wear.

Yes, in many cases the centre case gearbox can be replaced independently, making it a more cost-effective repair option.

Regular checks help prevent sudden lock failure, which can leave your door stuck or insecure. Learn more in Check This Before Your Next Let-In: Is the Door Gearbox Still Fit for Purpose.