Key Bumping
These two means of entry are becoming more common with burglars and they are something to be aware off. To understand Key bumping you need to know just how a cylinder lock works. Basically Yale, Chubb, Union etc. are brands of cylinder locks. They comprise of one cylinder inside another cylinder and the inner cylinder turns inside the outer one to unlock the latch. To stop the inner cylinder from turning there are upper , spring loaded pins that protrude into the inner cylinder stopping the inner cylinder from turning. This is called the shear line. The lower pins are different lengths and are lifted by the peaks on the key to the correct height to clear the shear line allowing the cylinder to turn.
Key-bumping basically puts a key with equal peaks into the lock, a sharp blow on the end of the key, whilst maintaining some pressure clockwise on the key, causes that pins to jump clear of the shear line and allows the inner cylinder to turn, opening the door. This is often the cause of entry when no other forced entry damage can be found and it only takes seconds to do. Most leading manufacturers of cylinder locks now produce replacement locks that are “bump proof” to British standards, look for the kite mark.

UPVC doors can offer an advantage over a wooden door simply because the more modern, better quality doors, have 5 point locking devices incorporated into their design. (Although these only work when used in conjunction with the key). If the handle is put up and the key isn't turned, the locks will release with pressure on the door frame with a screwdriver, from the outside. Please be warned, I have been to many burglaries with the householders were sleeping upstairs and thought putting the handle up was all that was needed . I do not doubt I will attend more in the future.

 I have seen some UPVC doors shatter with one blow from a door enforcer. On the other hand, I have also seen a UPVC door stand up to multiple strikes with an enforcer, almost 40 strikes. In fact the door didn't fail, the frame came away from the surrounding brickwork.

UPVC doors use Oval or Europe Profile locks and patio doors are high on the list of entry points. These locks can also be bumped but are more susceptible to “snapping” 

Lock Snapping
Again, Most leading manufacturers of locks now produce replacements that are “snap proof” The have a weak groove before the locking mechanism so that if an attempt is made to “snap” it, it breaks before the lock and then the rear lock cannot be accessed. I would recommend using an accredited M.L.Assoc or UK.LAssoc locksmith to check your locks or fit replacements. Look for the British Standard Kitemark.
These locks are basically two locks joined end to end. A key will turn the lock from the outside and there can be a key or thumb turn on the inside. Looking at the pictures below you can see there is a securing hole between the two locks, this causes a very weak point in the lock. The lock protrudes either side of the door and the protrusion is taken up by the handle plate. The plate is usually made from a thin metal and can be bent out of the way to expose the lock. A claw hammer strike or pressure from a screwdriver can snap the lock in half. The the outer half can be withdrawn giving the offender access to the inner lock that he can turn with a screwdriver.
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