These door locks work on most wood, glass, plastic and metal surfaces. No tools required for installation. Simply remove the pre-installed industrial tape carrier. An extra piece of soft TPR rubber is placed on the contact surface to protect doors and windows from scratches. It is very easy to use and for adults, but complex enough for children and pets can't do it all. Non-toxic and tasteless. These lenses are absolutely safe for children and durable enough to ensure your children's safety. [Size] 3.8*7CM thickness 0.6CM (error 2MM)