Firstly sash and dead locks come in either a 5 Lever or 3 lever option.
5 Lever Locks
5 lever locks use 5 levers. These levers are moved into position when the key is entered and turned in the lock. Once shut, you can't open the lock again from the outside without the key.
5 Lever locks are specified by insurance companies and are usually fitted on external entrance doors. Never try to fib your insurance company by telling them you have 5 Lever locks that are insurance rated fitted, if indeed you do not. A BS3621 lock will always be stamped with the British Standard 3621 Kitemark (normally on the face plate of the locking mechanism). An example of this can be seen below:
External entrance doors are usually more vulnerable to attack and so may be seen as a greater security risk so make sure insurance approved 5 Lever locks are fitted with the BS3621 stamp. A few examples within our store are the 5 Lever Insurance rated sash lock ref:JL127 and Dead lock version ref:JL117. Both are available with either satin stainless steel or polished brass face-plates.
3 Lever Locks
3 lever locks work in similar way to the above but with 3 levers and is used when less security is needed.
These are generally fitted internally as insurance rated locks are not generally required in private domestic properties. For example you would usually fit 3 Lever locks in the door leading from your house in to a garage, or if you wish to pop a lock on a bedroom door for extra privacy then 3 Lever locks will suffice. All locks are usually supplied with a couple of keys as standard.