A double knob cylinder is a type of lock that is used to secure doors or windows. It consists of two cylinders that are installed on both sides of the door or window, so that the door or window can be opened from both sides with a key or with a knob. Double knob cylinders are often made of steel or brass and are designed to be strong and durable. They are often used on doors that are accessible from the outside, such as exterior doors, to prevent someone from unwantedly opening the door without a key. Double knob cylinders can also be used on windows that are accessible from the outside, such as ground floor windows or windows that are easily accessible from the outdoors. Double knob cylinders provide an extra layer of security against break-ins and can help make your home or building safer.