The Ivess Lock is a security device which prevents patio doors from being lifted off its rails from the outside allowing access to your home. The simply installed device is a keyless locking system that improves home security in minutes. The placement and angle of the locking pin prevents the door from being lifted up and also prevents the door from being pulled out. The more upward pressure that is exerted on the door the tighter it gets in the locking engagement. Simple to operate. Easy to use handle knob. The spring is not too strong to pull. As Featured On Dragons' Den.