This configuration is common for UPVC doors and offers a balance of security and convenience. The key cylinder on the outside provides security against unauthorized entry, while the knob on the inside allows for easy manual locking and unlocking from within.

Here are some key aspects of this type of lock on a UPVC door:

• Multi-point Locking System: UPVC doors often feature a multi-point locking system that engages several bolts or hooks into the frame when the handle is lifted and the lock is engaged. The key cylinder and interior knob control the central mechanism of this system.
• Euro Cylinder Lock: The key cylinder is likely a Euro cylinder lock, which is a common type used in UPVC doors. These cylinders come in various security levels, including anti-snap, anti-drill, and anti-pick features.
• Handle Operation: The double handle likely means there’s an external handle for pulling the door and an internal handle connected to the locking mechanism. Lifting the handle often engages the multi-point locks before the cylinder is turned with a key or the knob.
• Security: The combination of a multi-point locking system and a keyed cylinder provides a good level of security for UPVC doors.