What's the name of the chain lock at the door? Where to buy it? How to install it?

First, the metal anti-theft chain is installed on the inside of the door, which can prevent the person who opens the door from being attacked by the outside world. Ordinary anti-theft chains can be bought in the building materials market and online shopping.

Second, the installation of the anti-theft chain is relatively simple. Use an electric drill to open holes in the door body and door frame, and use it to fix it.