Most UPVC doors use a type of lock called a Euro cylinder. I estimate less than 10% of houses in my area have BS kitemarked cylinders. The bulk of the other 90% of locks are to be frank ….. rubbish.
BS locks can also have additional ratings or certifications such as 1 to 3 stars, or the Sold Secure Diamond.
Below is a video of a high end BS cylinder. We supply and fit these Ultion locks if the customer wants one of the strongest locks available.
An important thing to consider is the lock length. The lock should not be sticking out of the exterior handles more than a few mm, ideally it should be flush. A lock that is too long on the outside leaves you more vulnerable to burglary.
Another common mistake you’ll see it the handles fitted the wrong way. If your screw holes are on the outside of the door then they’ve been fitted incorrectly. Again this is a security weakness.