One of the simplest types of door latches is the cabin hook latch. This consists usually of a short, arched metal rod attached to one side of the door, and a metal ring attached to other door frame. The metal rod, then, is inserted into the metal ring to keep the doors closed. In some cases, it is also used to keep the doors constantly open, with a metal ring fastened to a wall. This door latch does not provide as much security as other modern latches.
Another simple kind of door latch is the spring latch. It also consists of two parts. Traditional spring door latches have cords attached to the metal bolt in order to manually retract it and insert it in the metal hole attached to the door frame. Modern latches, however, have slanted bolts designed to automatically retract when the door is pushed. For more protection, these latches can only be released manually by turning the handle.
One modern type of door latches is the sliding door latch. One sliding door is usually attached with the metal bolt and the handle, and the other sliding door is built with a metal notch to contain the bolt. When the sliding doors are pushed together, a person can turn the handle to release the bolt and lock the doors. These latches are especially safe for when transparent sliding doors are near the outdoors, in order to prevent intruders and burglars. They can also keep out bugs and insect while still letting in needed sunlight.
One of the more secure door latches is the deadlatch. The deadlatch looks like a metal box with a handle on one of its surfaces and a keyhole on the opposite surface. Inside the box is one or two bolts that automatically retract when the door is closed. For more protection, the deadlatch also has a lock system that permanently locks the metal bolt in place—even a key cannot unlock it. Some deadlatches feature extra-long bolts that can only be retracted by several turns of the key, making it more secure.
Door latches can also be operated electronically, as in the case of an electric door latch. This type can be unlocked not with a key, but with a programmed code. Some electronic latches can even be connected to an alarm system that notifies the police or the homeowners if the wrong code is inputted several times. Door latches like these are installed in expensive residences and facilities that need tight security.
