The anti-theft chain buckle is situated near the back of the door, not too far from the edge of the door. One end of the chain slides into the chain buckle on the door's back, while the other end is firmly attached to the door frame. By hanging the anti-theft chain, one can only open the door to a maximum of 5 to 8 centimeters, making it impossible for people to pass through, let alone reach the chain buckle. With this feature, it prevents sudden attacks from intruders when the owner opens the door. It is worth noting that the sliding chain can be easily cut with tools such as metal shears; hence, the anti-theft door chain cannot be solely relied on as a door lock. It is only meant to be an auxiliary tool to provide an extra layer of security, and that is why it is called a "careful lock" to remind people to be cautious.