A lock bar is flat or round extension that transfers the rotary action of a central lock to the frame of a door. The term is also applied to a single length or telescopic bar used as a separate locking mechanism for sliding doors. In the case of a transfer mechanism, the lock bar is typically hinged to a rotary lever on the lock mechanism. When the lock is activated, the bar is pushed outward to lock into recesses in the frame of the door. Sliding door lock bars are simple hinged or removable bars which are fastened to the door frame and lock onto the sliding door, thereby preventing it from opening or being lifted from its track.
The term lock bar may be used to describe both rotary extension bars and sliding door lock bars. Rotary lock bars are commonly used in low security applications such as metal stationary cabinets and in high security entrance door mechanisms. These locking bars are typically flat or round lengths of steel attached to a rotary cam on the central locking mechanism. The bars may attach to the sides of the cabinet frame or travel vertically to lock into the top of the frame. There are typically only two locking bars in this type of mechanism.
High security entry door lock bar arrangements are substantially stronger and may feature up to seven separate bars per door. Unlike cabinet lock bars which have very little if any support inside the door itself, high security lock bars usually pass through several close tolerance machined bushes within the door. Another difference between the two systems is that cabinet lock bars are generally exposed behind the door while the high security variants are totally enclosed within the door. The average lock bar in this type of system is also generally round in profile and a lot stronger than the cabinet versions. These systems will generally lock into both sides and the top of the frame and into the floor.
Conventional sliding door locks are notoriously weak; more often than not they are first choice of point of ingress for thieves. One of the more efficient ways of adding additional security to sliding doors is the installation of a lock bar. This device is a simple hinged, single length or telescopic steel bar that attaches to the door frame or wall and locks onto the door. When locked in place, the door cannot be pushed open and is also more difficult to lift out of its tracks. When the door is opened, the bar is either unlocked and telescoped closed or, in the case of single length removable bars, removed from the frame hinge and stowed away.