Devices that allow to fix the door to the door frame and prevent penetration of the room without a key. Depending on the installation method distinguish padlocks, mortise and others.
A variety of mechanisms lock security. Working part is a cylinder which can be rotated only when in the cylinder hole is inserted key.
Standalone design padlocks allows you to completely separate it from the fixing elements (lugs on the door leaf and the door frame, the bike frame and the fixed bearing).
Devices that allow to fix the door in the closed position. The latch is operated by pressing on the door handle. There are latches with additional fixing (locking) the door in the closed position and without it.