This revolutionary locking system, patented by Kong in 1985, takes its name from the unique shape of the connection between the gate and the body of the connector that resembles a door keyhole. The real advantage of this system is that there is absolutely no need for any teeth on the body of the carabiner or on the gate which is completely cylindrical. This removes any points where the rope or webbing could get snagged, all the sharp edges found on traditional gates have been eliminated for comfort and ease of use.